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COLLEGE  of  MINING 

DEPARTMENTAL 
LIBRARY 


BEQUEST  QF 


.*..  -  SAMUELBENEDICTCHRISTY 

PROFESSOR  OF 

MINING  AND  METALLURGY 
1885-1914 


*  ••  «W»I8TY. 


THE 


MANAGEMENT  OF  STEEL. 


BY 

GEORGE  EDE; 

EMPLOYED  AT  THE   ROTAL  GDN  FACTORIES'  DEPARTMENT,  WOOLWICH  I 

ARSENAL. 


jFourtJ)  BUttton,  lUfatsrtJ  antr 


NEW  YORK: 

D.  APPLETON  &  CO.,  443  AND  445  BROADWAY, 


Ts 

£3 


MIMIN«  o*  rr, 


PBEFAOE. 


IT  has  long  been  acknowledged  that  a  small 
practical  work  upon  the  forging,  annealing,  hard- 
ening, and  tempering  of  steel,  and  the  case-harden- 
ing of  iron,  etc.,  was  wanting  amongst  us ;  and  it 
was  with  the  object  of  assisting  to  supply  this 
want,  that  I  contributed  my  mite  in  publishing 
and  giving  my  experience  in  the  small  work  on  the 
Management  of  Steel.  How  far  my  efforts  have 
succeeded  in  supplying  this  want,  I  am  not  about 
to  say ;  but  the  flattering  reception  and  high  praise 
it  has  received  in  passing  through  three  editions, 
has  induced  me  to  issue  a  much  larger  work  in  a 
revised  form.  I  gave  it  the  tijtle  of  "The  Man- 
agement of  Steel "  when  I  published  the  first  edi- 
tion, simply  because  I  could  think  of  no  other 
better ;  and  I  continue  the  name  because  I  am  still 
unable  to  think  of  one  more  suitable.  In  this 
present  attempt,  my  aim  has  been  to  write  a  work 
which  would  be  found  as  useful  to  the  novice  or 


4  PREFACE. 

amateur  mechanic  as  to  the  practical  man ;  and  I 
have  endeavored  to  word  the  subject  in  such  a 
homely  style,  that  persons  totally  unacquainted 
with  the  processes  on  which  it  treats  will  be  able 
to  judge  for  themselves  as  to  the  reasonableness  of 
my  remarks.  It  treats  upon  the  manufacture  of 
iron  and  steel,  the  choosing  of  steel  for  tools,  for- 
ging iron  and  steel,  annealing  cast  iron  and  steel, 
hardening  and  tempering  of  cast  iron  and  steel, 
expansion  and  contraction  of  steel,  shrinking  of 
iron  and  steel,  and  the  case-hardening  of  wrought 
iron,  also  the  toughening  of  mild  cast  steel  for 
guns,  shot,  railway  bars,  etc. 

It  will,  I  believe,  be  found  in  the  future  an  ines- 
timable treasure  to  those  young  mechanics  who 
may  possess  it ;  for,  in  my  opinion,  if  young  ap- 
prentices were  taught  to  make  themselves  better 
acquainted  with  the  materials  they  work  upon,  like- 
wise the  materials  from  which  their  tools  are  made, 
and  the  management  of  that  material,  the  advance- 
ment of  the  sciences  would  be  greatly  hastened,  as 
this  knowledge  would  increase  the  powers  of  the 
head  to  contrive,  and  the  powers  of  the  hands  to 
execute.  The  inventions  which  become  publicly 
known  are  few  in  comparison  with  those  which 
spring  up  in  the  minds  of  ingenious  mechanics 
and  perish  with  the  hour  that  gave  them  birth, 
through  the  want  of  a  better  knowledge  of  the 


PREFACE.  5 

properties  of  materials.  Although  this  work  is  not 
calculated  to  supply  all  this  knowledge,  still  my 
aim  has  been  to  be  of  use,  and  to  contribute  toward 
it.  I  cannot  expect  that  it  will  entirely  satisfy  the 
wishes  of  all  my  readers;  but  I  have  dwelt  at 
greater  length  on  those  subjects  which  I  have  con- 
sidered from  my  own  experience  to  be  the  most 
important,  and  I  sincerely  hope  that  its  contents 
may  prove  of  some  benefit  to  those  who  may  favor 
me  by  an  impartial  perusal. 

GEORGE  EDE. 
1  Raglan  Road*  Plumstead. 


CONTENTS. 


CHAPTER  I. 


MANUFACTURE   OF   IRON. 

f 
PAGE 

Wide  diffusion  of  iron — State  in  which  found — Not  of  a  noxious 
nature — Specific  gravity — Properties  of  wrought  iron — Used 
for  mechanical  purposes  in  three  states — Difference  of  iron 
in  the  three  states. 11 

Extracting  the  ores — Roasting — Smelting — Different  qualities 

of  pig  iron  used  for  different  purposes 16 

Refining — Puddling — Rolling  into  bars. 19 

Qualities  of  wrought  iron — Effects  of  sulphur  on  hot  iron 23 


CHAPTER  II. 

MANUFACTURE   OF   STEEL. 

Steel — How  formed — Principle  of  Mr.  Bessemer's  process — 
Converting  iron  into  steel  by  cementation — Change  in  the 
properties  of  iron  by  the  penetration  of  carbon 25 

Mode  of  preparing  tilted,  spring,  shear,  and  cast  steel 31 


O  CONTENT,  b. 

CHAPTER  m. 

CHOOSING   OF   STEEL. 

PAGE 

Methods  of  testing  the  true  quality  of  tool  steel— Not  necessary 

to  subject  it  to  chemical  analysis 34 

Appearance  of  tool  steel  on  fracture  in  a  hard  and  soft  state — 

Use  of  aquafortis  to  distinguish  iron  from  steel 39 


CHAPTER  IV. 

FORGING  AND   WELDING   IRON   AND   STEEL. 

The  forge — Welding — Degrees  of  heat — How  distinguished... .  41 

Fuel  for  forging  iron  and  steel .....-.' 42 

Heavy  iron  forgings,  how  made  up — Remarks  on  the  mingling 

of  the  fibres  in  the  scrap  iron 43 

Suggestions  for  improvements  in  forging  wrought  iron  gun- 
blocks :.....  47 

Suggestions  for  improvements  in  casting  and  forging  steel  gun- 
blocks  61 

Smith's  forge — Tools  used  in  forging. 52 

Building  and  management  of  the  fires — Effects  of  overheating 
steel — The  heat,  how  judged  of — Tenacity  and  elasticity 
of  steel  increased  by  hammering 54 

Upsetting — Welding  iron  to  iron — Steel  to  iron--— Steel  to  steel 

— Use  of  sand,  borax,  and  sal-ammoniac  in  forging 64 

Cutting  bars  of  steel  into  short  lengths 68 


CHAPTER  V. 

ANNEALING. 

Steel — Cast  iron — Copper 71 


CONTENTS. 


CHAPTER  VI. 

HARDENING  AND   TEMPERING   OF  STEEL. 

PAGE 

Introductory  remarks — Hints  to  the  mechanic  on  the  manufac- 
ture of  tools  to  be  hardened 77 

Water  not  essential  for  hardening  steel— Degrees  of  temperature 

required  for  hardening  steel — Mode  of  applying  the  heat. .     91 

Art  of  tempering — Colors  to  be  observed — Mode  of  applying  the 

heat — Tempering  steel  with  tallow  and  oil 95 

Rules  to  be  observed  previous  to  immersion — Temperature  of 
water — Hardening  in  mercury,  etc. — Mode  of  applying 
carbon  to  steel 106 

Advantage  of  hardening  tools  from  the  forge — Results  of  im- 
perfect cooling,  flaws,  breakages,  etc 109 

Hardening  and  tempering  circular  cutters,  dies,  bushes,  collars, 

ring  gauges,  etc 119 

Various  methods  of  hardening  and  tempering  screw-taps,  hobs, 

screw-dies,  chasers,  and  screw-plates 140 

Various  methods   of  hardening  and  tempering  saws,  rimers,     » 
small  drills,  gouge-bits,  centre-bits,  countersinks,  gimblets, 
bradawls,  etc 157 

Heating  a  steel  plate  in  hot  lead 171 

Hardening  and  tempering  drifts,    large  drills,  and  chipping- 

chisels 178 

Method  to  give  to  steel  a  superior  hardness  without  the  use 
of  mercury  or  saline  liquids — Hardening  and  tempering 
spiral  and  other  kinds  of  springs— Angled  cutting-edges 
of  tools  and  speed  of  lathe 184 


CHAPTER  VII. 

EXPANSION   AND   CONTRACTION   OP   STEEL. 

Causes  of  expansion  and  contraction — Various  methods  of  con- 
tracting holes  in  iron  and  steel 188 


10  CONTENTS. 

CHAPTER  VIII. 

CASE-HARDENING  WROUGHT   IRON. 

PAGE 

By  prussiate  of  potash — Animal  charcoal 198 

CHAPTER  IX. 

TOUGHENING   OP   STEEL   IN   OIL. 

Railway  bars — Gun-blocks — Mode  of  heating  gun-blocks — Tem- 
perature required — Fuel  employed — Manner  in  which  the 
cooling  is  performed— Change  which  takes  place  in  the 
steel  by  the  operation — Cause  of  the  change — Shot  for 
piercing  iron  and  steel  clad  structures — Suggestions  for 
improvements  in  their  manufacture 208 

CONCLUSION .  220 


THE 

MANAGEMENT    OF    STEEL. 


CHAPTER  I. 

MANUFACTURE  OF  IRON". 

IT  was  not  my  original  intention  to  have  ex- 
plained the  manufacture  of  iron,  or  the  converting 
of  iron  into  steel,  or  of  casting  steel  into  ingots ; 
more  especially  when  so  much  has  been  already 
written  upon  these  subjects  by  those  better  quali- 
fied than  myself;  but,  in  answer  to  inquiries,  and 
knowing  that  my  little  work  is  not  complete  with- 
out it,  especially  as  it  is  likely  to  come  into  the 
possession  of  many  whom  books  of  a  superior  class, 
never  reach,  on  account  of  the  high  price  at  which 
they  are  sold,  I  have  resolved  in  this,  the  fourth 
edition,  before  explaining  the  processes  of  harden- 
ing and  tempering  steel,  to  introduce  a  slight 
sketch  of  the  processes  by  which  the  material  is 
prepared. 

Iron  is  a  mineral,  and  in  its  native  state  is 
called  iron  ore ;  it  is  probably  the  most  abundant, 
useful,  and  valuable  of  all  the  metals ;  in  fact,  its 


12  MANUFACTURE   OF  IRON. 

value  is  beyond  .all  estimate.  In  nearly  every 
country  011  the  face  of  the  globe,  more  or  less  of  it 
has  been  discovered,  and  there  is  no  doubt  that  it 
exists  in  all  parts  of  the  world ;  and,  from  its  ex- 
tensive and  diversified  utility,  it  is  one  of  the  most 
useful  substances  known.  It  is  a  metal  of  great 
antiquity,  and  it  is  quite  probable  that  it  has  been 
known  and  used  from  the  earliest  ages.  But  the 
circumstances  which  first  led  to  the  discovery  of 
the  ores,  and  the  processes  for  reducing  them  into 
the  pure  metal,  I  must  leave  to  the  antiquarian. 
It  would  also  be  vain  or  idle  of  me  to  attempt  to 
describe  the  numberless  uses  to  which  iron  is 
applied,  when  they  are  so  well  known.  Iron  is 
seldom  found  pure — that  is,  it  is  the  most  difficult 
metal  to  obtain  in  a  state  fit  for  use :  but  it  com- 
monly consists  of  an  oxide  of  the  metal — that  is,  it 
is  in  combination  with  oxygen.  It  is  generally 
mixed  with  substances  such  as  clay,  flint,  and  other 
impurities ;  and,  when  combined  with  these  sub- 
stances in  such  quantity  as  to  be  worth  separating, 
the  substance  is  called  ironstone,  or  iron  ore,  and  it 
is  from  this  that  the  pure  metal  is  extracted.  The 
origin  of  the  ores  is  beyond  our  knowledge ;  but,  as 
an  instance  of  the  great  Creator's  wisdom  in  pro- 
viding for  the  comforts  and  welfare  of  mankind, 
those  ingredients  requisite  for  fusing  and  converting 
the  ores  into  the  pure  metal,  such  as  coal  and  lime- 
stone, are  generally  found  in  the  same  localities  as 
the  iron  ores ;  and  in  those  countries  where  coal 
does  not  exist,  wood  is  found  in  abundance. 

Iron  appears  to  be  the  only  metal  whose  solutions, 


MANUFACTURE   OF    IRON.  13 

or  combinations  witli  oxygen,  are  not  of  a  noxious 
nature.  Mineral  waters  containing  iron  strengthen 
and  increase  muscular  action ;  and  in  chalybeates, 
form  the  best  tonics  medicine  can  boast. 

Iron  is  nearly  eight  times  heavier  than  water ; 
its  specific  gravity  is  about  7.TY.  Its  texture  is 
fibrous ;  it  is  of  a  bluish- white  or  peculiar  gray 
color,  and  is  susceptible  of  a  high  polish.  It  is 
hard  and  sonorous;  it  also  strikes  fire  with  flint* 
and  is  highly  elastic.  For  instance,  if  a  bar  is 
bent  by  pressure  applied  to  it,  and  if  this  pressure 
does  not  exceed  a  certain  quantity,  the  bar  will  re- 
sume its  original  form  when  the  pressure  is  re- 
moved. It  is  also  malleable,  which  is  the  property 
of  extending  or  spreading  under  the  hammer  with- 
•out  cracking,  but  less  so  than  gold,  silver,  or  copper. 
It  is  also  very  ductile,  a  property  similar  to  malle- 
ability, whereby  it  may  be  drawn  out  into  wire 
without  breaking.  Its  tenacity  is  very  great,  a 
property  which  enables  it  to  sustain  a  very  great 
pressure  or  force  without  crushing  or  breaking.  In 
a  cold  state  it  is  hard  and  stubborn,  but  at  a  red 
heat  it  is  soft  and  pliable  ;  and,,  at  a  white  or  spark- 
ling heat,  it  may  be  welded  either  to  itself  or  to 
steel.  This  is  one  of  its  greatest  advantages.  IVhen 
two  pieces  of  iron  are  equally  heated,  nearly  to  a 
state  of  fusion,  they  appear  to  be  covered  with  a 
strong  glaze  or  varnish.  "When  brought  together, 
they  may  be  united  by  repeated  blows  of  the  ham- 
mer, or  under  pressure,  and  the  union  will  not  be 
visible.  Although  fire  makes  it  soft  and  flexible, 
so  that  it  can  be  easily  bent,  cut,  punched, 


14  MANUFACTURE   OF   IEON. 

hammered,  welded,  and  fashioned  to  any  desired 
shape,  the  difficulty  of  melting  malleable  iron  is 
very  great.  It  requires  the  greatest  heat  of  a  wind 
furnace  ;  but  the  nearer  it  approaches  to  fusion,  the 
more  malleable  and  ductile  it  becomes. 

Iron  is  employed  for  mechanical  purposes  in 
three  states ;  namely,  that  of  cast  iron,  wrought 
iron,  and  steel. 

Cast  iron  is  the  metal  in  its  first  state,  rendered 
fusible  by  its  combination  with  those  two  sub- 
stances which  chemists  distinguish  by  the  name  of 
carbon  and  **gygpi-  Cast  iron  is  that  which  results 
from  the  fusion  of  the  iron  ore  with  charcoal,  coal, 
or  coke.  Cast  iron  contains  more  carbon  than  steel ; 
and,  though  it  is  principally  in  the  superabun- 
dance of  its  carbon  that  it  differs  from  steel,  still 
this  is  not  the  only  cause  of  the  difference  between 
the  properties  of  iron  in  the  two  states ;  for  cast 
iron  contains  other  impurities,  which  lessen  the 
cohesion  of  its  particles — impurities  which  steel  is 
freed  from.  From  its  carbon,  however,  some  cor- 
respondence in  their  characters  is  found  to  exist ; 
thus,  some  kinds  of  cast  iron  admit  of  being  made 
hard  or  soft,  nearly  in  the  same  manner  as  steel ; 
like  steel,  it  assumes  different  degrees  of  hardness, 
according  to  the  rapidity  with  which  the  pieces  are 
allowed  to  cool.  To  harden  cast  iron,-  it  requires 
to  be  heated  to  a  higher  degree  of  heat  than  that  to 
which  steel  is  subjected  for  the  same  purpose,  and 
then  suddenly  cooled  in  cold  water,  which  imparts 
to  it  whiteness  of  color,  and  brittleness  and  closeness 
of  texture.  Cast  iron,  when  once  hardened,  will  not 


MANUFACTURE   OF   IRON.  15 

admit,  like  steel,  of  that  hardness  being  reduced 
by  various  gradations  to  any  specific  degree  (called 
tempering);  to  soften  materially,  it  must  be  sub- 
mitted for  some  time  to  a  whitish  heat,  and  then 
very  gradually  cooled.  Cast  iron  may  be  termed 
an  impure  carbonized  iron. 

Wrought  iron  is  the  cast,  or  pig,  iron,  freed  from 
carbon  and^oxjgfiH,  and  maybe  termed  a  nearly   Jt/, 
pure  decarbonized,  iron,  and,  which  has  previously 
been  remarked,  is  hardly  fusible. 

Steel  is  a  combination  of  iron  and  carbon,  in 
which  the  proportion  of  carbon  is  very  small,  vary- 
ing from  one  to  two  "per  cent.,  and  occupies  an  in- 
termediate position  between  cast  and  wrought  iron. 
Steel  is  less  fusible  than  cast  iron,  but  much  more 
so  than  wrought  iron. 

We  will  now,  for  a  short  time,  leave  the  subject 
of  the  properties  of  the  iron  in  these  three  statesj 
and  commence  with  the  manufacture  of  iron.  By 
so  doing,  I  presume^  the  whole  subject  will  be  the 
better  understood. 

From  excavations  called  mines,  by  drainage,  the 
employment  of  suitable  machinery,  and  the  industry 
of  the  miner,  the  ore  is  extracted  in  a  very  rough 
state  from  the  bowels  of  the  earth.  It  is  this  cir- 
cumstance which  ranks  it  among  minerals.  The 
first  process,  after  the  ore  has  been  taken  from  the 
vein,  is  to  calcine  or  burn  the  stones  (a  process  call- 
ed roasting),  in  order  to  expel  the  water,  sulphur, 
arsenic,  and  other  impurities  with  which  the  ores 
are  combined,  before  being  east  into  the  smelting- 
furnace.  The  roasting  is  effected  by  kindling  large 


16  MANUFACTURE   OF   IRON. 

fires  in  the  open  air,  and  spreading  upon  the  fires 
layers  of  ironstone  mixed  with  cinders,  coke-dust, 
and  small  coal,  or  other  combustibles,  such  as  wood 
and  charcoal.  Sometimes  the  roasting  is  performed 
in  a  kiln.  The  fuel  and  ironstone  are  put  in  at  the 
top,  and  the  roasted  metal  is  taken  out  at  the  bot- 
tom. The  loss  of  weight  by  the  process  of  roasting 
is  considerable,  and  in  proportion  to  the  quality  or 
purity  of  the  ore ;  the  more  impure,  the  greater  the 
loss  of  weight.  The  process  of  roasting  in  the  open 
air. was  at  one  time  almost  universally  adopted; 
but  some  years  ago,  a  Scotch  gentleman,  Mr.  Neilson, 
introduced  the  hot  blast  for  smelting  the  ore — that 
is,  drying  and  heating  the  air  before  it  is  forced  into 
the  furnace.  This  invention  has  proved  very  val- 
uable and  economical.  Since  its  introduction,  the 
ore  and  fuel  are  frequently  used  in  the  raw  state, 
and  the  process  of  roasting  in  the  open  air  has  been 
t  abandoned  by  many  ironmasters. 

The  next  process  is  smelting  •  the  object  of  which 
is  to  produce  the  metal  in  a  purer  state,  and  to  form 
of  all  the  other  substances  (as  far  as  it  is  practicable) 
oxides  and  slags.  In  the  great  iron-works,  the  ore, 
broken  into  small  pieces  and  mixed  with  a  portion 
of  broken  limestone,  is  thrown  into  the  blast  or 
smelting-furnace  with  coke,  coal,  or  charcoal,  in  due 
proportion.  The  fire  is  raised  to  an  intense  heat  by 
the  combustion  of  the  fuel  and  by  the  forcing  in  of 
a  current  or  blast  of  air,  either  in  a  cold  or  heated 
state.  It  may  be  well  to  state  here,  that  earths 
when  alone  are  scarcely  alterable  by  the  most  in- 
tense heat.  Lime,  however,  although  very  infusible 


MANUFACTURE   OF   IRON.  17 

alone,  as  a  flux  promotes  the  fusion  of  the  other 
earths  which  the  ores  of  iron  contain.  If  slags  and 
metal  are  rendered  perfectly  fluid  they  will  separate, 
in  consequence  of  their  want  of  affinity  and  their 
difference  in  specific  gravity.  S"ow,  pure  lime  is 
very  seldom,  if  ever,  found  native,  but  always  in 
combination  with  acids,  particularly  carbonic  acid ; 
and  in  the  intense  heat  of  the  smelting-furnace  the 
limestone  parts  with  its  carbonic  acid,  and,  com- 
bining with  the  earthy  matters  of  the  ironstone, 
forms  with  them  a  liquid  slag.  The  metal,  as  it 
melts,  is  deoxidized,  and,  being  the  heaviest,  sinks 
by  its  own  gravity,  through  the  fuel,  to  the  bottom 
of  the  furnace ;  more  ore  and  fuel  are  supplied  from 
the  top,  and  the  operation  goes  on  until  there  is 
sufficient  metal  melted  to  constitute  what  is  termed 
a  charge,  which  rises  almost  to  the  aperture  of  the 
blast.  The  furnace  is  then  tapped  at  the  tap-hole, 
and  the  metal  run  off  into  moulds  ;  these  lumps  are 
called  pigs  of  crude  or  cast  iron,  and,  for  purposes 
where  hardness  without  flexibility  is  wanted,  the 
iron  in  this  state  is  extensively  used.  Of  course,  it 
will  be  necessary  to  remelt  it  to  cast  it  into  the 
required  form.  The  iron  in  this  state  varies  greatly 
in  quality,  as  may  easily  be  supposed,  from  the  dif- 
ference of  its  chemical  composition,  some  kinds  being 
much  purer  than  others.  The  quality  of  pig  iron 
varies  according  to  the  purpose  for  which  it  is  in- 
tended :  it  does  not  entirely  depend  upon  the  qual- 
ity of  the  ore,  but  partly  upon  the  purity  of  the  fuel 
and  the  treatment  it  undergoes.  The  quality  of  the 
iron  will  vary  with  the  qiianity  of  carbon  it  con- 


18  MANUFACTURE   OF  IRON. 

tains ;  and  those  who  are  acquainted  with  and  ac- 
customed to  the  smelting  operations,  can  generally 
form  an  opinion  as  to  the  state  and  quality  of  the 
metal  as  it  flows  from  the  furnace,  and  also  from  its 
appearance  when  broken. 

The  pig  iron  is  assorted  and  classed  by  the  iron- 
master as  Nos.  1,  2,  and  3,  and  differing  in  the 
amount  of  carbon  combined.  ~No.  1  is  most  highly 
carbonized,  No.  2  less,  and  ~No.  3  contains  the  least. 
No.  1  runs  so  fluid  as  to  be  the  most  suitable  for 
ornamental  work ;  it  runs  fine  enough  to  fill  the 
sharp  angles  and  figures  of  the  mould  into  which  it 
is  poured.  Cast-iron  cutlery  is  manufactured  from 
JSTo.  1,  and  the  carbon  subsequently  extracted  from 
the  articles.  This  is  done  by  heating  them  for  a 
considerable  time  in  a  furnace,  and  surrounding  them 
on  all  sides  with  some  substance  containing  oxygen, 
such  as  the  pure  oxide  of  iron,  or  any  earthy  in- 
fusible powders  free  of  sulphur.  The  articles  obtain, 
by  this  process  of  annealing  and  purifying,  a  con- 
siderable degree  of  malleability,  and  it  is  not  impos- 
sible to  render  them  capable  of  being  welded.  For 
large  works  or  castings,  which  require  great  strength, 
the  iron  which  contains  a  smaller  proportion  of  car- 
bon is  preferable ;  and  that  which  has  the  least 
carbon,  and  is  freest  from  other  impurities,  is  prob- 
ably the  most  suitable  for  the  manufacture  .  of 
wrought  iron.  It  may  be  observed,  that  the  whiter 
the  metal  the  harder  it  is  also. 

Cast-metal  articles  are  made  from  the  iron  just 
treated  of.  The  pig  iron  is  melted  at  the  founderies, 
and  runs  in  a  state  of  fusion  into  moulds,  either  direct 


MANUFACTURE    OF   IKON.  19 

from  the  furnace  by  channels  cut  in  the  sand,  or  into 
ladles  to  be  conveyed  to  the  moulds,  which  are  made 
of  either  iron,  sand,  or  loam,  according  to  the  re- 
quired shape  and  size.  The  moulds  (excepting  those 
made  of  iron)  are  generally  formed  by  means  of  a 
wood  or  iron  pattern;  which,  sunk  in  the  sand  and 
then  withdrawn,  leaves  a  cavity  of  the  desired  form, 
into  which  the  fluid  metal  is  run.  If  the  metal  is 
large  in  quantity,  it  is  agitated  by  the  workman  with 
an  iron  rod  in  order  to  consolidate  the  mass,  and  to 
get  rid  of  any  air  or  gas  which  may  be  confined  in 
the  metal ;  after  which  it  is  allowed  slowly  to  cool 
and  crystallize.  When  cold  the  castings  are  taken 
out.  It  is  a  curious  fact  that  if  the  rod  used  for 
agitating  the  metal  be  a  slender  one,  it  is  quickly 
converted  into  steel,  though  of  very  indifferent  qual- 
itp,  which  is  a  satisfactory  proof  that  cast  iron  con-1 
tains  carbon,  the  steel-making  principle. 

Having  stated  that  wrought  iron  is  nearly  pure 
decarbonized  iron,  it  remains  to  be  shown  in  what 
way  the  decarbonization  is  effected.  The  first  opera- 
tion for  producing  this  change  is  called  refining.  The 
pig  iron  is  remelted  in  a  furnace,  called  a  refining 
furnace,  and  kept  in  a  state  of  fusion  for  some  time, 
exposed  to  an  intense  heat,  and  a  blast  of  air  forced 
over  its  surface  in  order  to  remove  some  of  the  im- 
purities of  the  metal ;  it  is  then  run  out  of  the  fur- 
nace into  a  large  flat  mould,  and  acquires  the  name 
of  plate  metal. 

The  succeeding  process  is  called  puddling ;  the 
object  in  this  process  is  to  free  the  metal  of  its  carbon 
and  oxygen.  The  operation  is  performed  in  a  rever- 


20  MANUFACTTJEE   OF   IKON. 

beratory  or  puddling  furnace,  where  the  cast  metal 
is  again  reheated,  and  converted  into  wrought  iron 
by  keeping  it  in  a  state  of  fusion  for  a  considerable 
time,  and  repeatedly  stirring  it  in  the  furnace,  by 
means  of  tools,  through  a  small  hole  in  the  furnace, 
provided  for  that  purpose ;  the  whole  of  the  metal 
is  thus  exposed  to  the  action  of  the  oxygen  passing 
over  it  from  the  fire,  at  the  same  time  adding  matters 
capable  of  yielding  oxygen.  "When  the  whole  mass 
has  received  an  equally  high  temperature,  the  oxygen 
and  carbon  which  it  contains  unite  and  fly  off  in  the 
state  of  carbonic  acid  gas,  and  as  this  takes  place 
the  iron  becomes  more  infusible ;  it  gets  thick  or 
stiff  in  the  furnace,  and  grows  increasingly  so  until 
it  loses  nearly  all  fluidity,  and  the  workmen  know 
by  this  appearance  that  it  is  time  to  submit  it  to  the 
action  of  the  hammer,  or  the  pressure  of  a  machine 
called  a  squeezer.  The  workman  then  divides,  by 
means  of  his  tools,  the  contents  of  the  furnace  into 
several  parts,  and  forms  them  into  separate  balls. 
The  balls  being  removed  from  the  furnace,  they  are 
each  subjected  to  a  number  of  blows  from  a  heavy 
steam  hammer  (called  shingling),  or  to  an  intense 
pressure  by  a  machine  called  a  squeezer,  by  which 
the  parts  which  still  partake  of  the  nature  of  crude 
or  cast  iron  so  much  as  to  retain  the  fluid  state  are 
forced  out,  and  the  balls  brought  to  an  oblong  shape, 
which  is  a  shape  more  convenient  for  going  through 
the  rollers.  The  balls,  after  having  undergone  the 
first  process  of  shingling  by  the  hammer,  or  the 
squeezer,  or  any  of  the  other  machines  invented  for 
the  purpose,  are  then  called  blooms.  The  bloom  is 


MANUFACTURE   OF  IRON.  21 

then  raised  to  the  welding  temperature  in  a  reheat- 
ing furnace,  and  again  submitted  to  the  action  of 
the  hammer,  or  it  is  at  once  passed  through  large 
rollers  having  on  their  surfaces  a  series  of  grooves 
varying  in  size,  and  when  passed  through  these 
grooves  in  succession,  the  bloom  is  reduced  and 

O  ' 

elongated  to  a  flat  bar,  to  the  required  width  and 
thickness.  The  bars,  after  they  have  passed  through 
these  rollers,  are  cut  into  convenient  lengths  by  the 
shears;  they  are  then  piled  or  fagoted  together 
into  convenient  heaps.  Several  of  these  piles  or 
heaps,  each  of  which  is  composed  of  five  or  six  J)ars, 
are  placed  at  once  in  the  furnace,  and,  when  heated 
to  the  welding  temperature,  they  are  taken  out 
separately,  and  are  again  passed  through  the  rollers 
to  reduce  it  to  the  form  of  a  bar ;  the  grooves  in 
these  rollers  differing  according  to  the  shape  the 
bars  are  required,  so  that  either  round,  square,  flat, 
or  various  other'  shapes  may  be  produced  at  the 
pleasure  of  the  maker.  Sometimes,  in  order  to  pro- 
duce a  superior  kind  of  iron,  the  cutting  and  welding 
and  rolling  is  again  repeated.  "When  charcoal  is 
used  as  fuel  in  place  of  coal,  or  coke,  for  the  manu- 
facture of  iron,  a  superior  kind  of  iron  is  obtained  ; 
but,  owing  to  the  expense  of  charcoal,  it  is  obvious 
that  the  iron  thus  made  is  more  expensive.  The 
bars  having  received  their  various  shapes  from  the 
rollers,  are  then  straightened  and  sheared  to  the  re- 
quired sizes,  weighed  and  ready  for  sale.  By  these 
processes  the  metal  is  thus  converted  from  a  fusible, 
hard,  and  brittle  substance,  into  a  tough  and  elastic 
bar ;  in  fact,  it  has  been  rendered  malleable,  ductile, 


22  MANUFACTUKE   OF   IKON. 

more  closely  compacted,  of  a  fibrous  texture  which. 
is  hardly  fusible,  and  for  purposes  where  lightness, 
strength,  and  durability  is  wanted,  it  is  more  exten- 
sively employed  than  cast  iron.  In  this  state  it  is 
known  in  commerce  by  the  name  of  bar,  or  wrought 
iron  ;  and  it  may  now  be  considered  a  nearly  pure 
decarbonized  iron,  and  is  ready  for  the  smith,  and 
the  converter,  to  be  made  up  or  fashioned  into  the 
thousand  varieties  of  articles  from  a  needle  to  Sir 
William  Armstrong's  six-hundred  pounder. 

The  loss  of  weight  sustained  by  iron  in  the  pro- 
cess of  refining,  paddling,  hammering,  and  rolling,  is 
considerable,  generally  amounting  to  one-fourth,  and. 
sometimes  to  one-half.  Forged  or  wrought  iron, 
like  cast  iron,  varies  greatly  in  quality,  according  to 
purity  and  treatment  in  its  manufacture.  Thus, 
some  kinds  are  only  tough  and  malleable  at  certain 
temperatures,  whilst  other  kinds  are  tough  and  mal- 
leable at  all  temperatures ;  or,  in  other  words,  both 
when  the  iron  is  hot  and  when  it  is  cold.  There  are 
four  kinds  of  iron  which  require  most  to  be  treated 
of,  the  other  kinds  having  qualities  occupying  inter- 
mediate positions  between  these  varieties.  Iron 
which  is  tough  and  malleable  at  all  temperatures  is 
the  .best  and  most  useful,  as  it  may  be  bent  in  any 
direction  without  breaking,  both  when  it  is  hot  and 
when  it  is  cold.  It  may  be  known  generally  by  the 
equable  surface  of  the  forged  bar,  which  is  free  from. 
cross  fissures,  or  cracks  in  the  edges,  and  by  a  clear, 
white,  small  grain,  or  rather  fibrous  texture.  The 
best  and  toughest  iron  is  that  which  has  the  best 
welding  properties,  and  which  bears  the  highest  heat 


MANUFACTURE   OF   IRON.  23 

without  injury,  and  which  has  most  fibrous  texture, 
and  is  of  a  clear  grayish  color.  This  fibrous  ap- 
pearance  is  given  by  the  resistance  which  its  particles 
make  to  separation.  The  next  best  jron,  which  is 
also  tough  and  malleable  in  all  temperatures,  and 
which  bears  a  moderately  high  degree  of  heat  with- 
out injury,  and  which  has  also  good  welding  prop- 
erties, has  a  texture  consisting  of  clear,  whitish, 
small  grains  intermixed  with  fibres.  Another  kind 
is  tough  when  it  is  heated,  but  brittle  when  cold,  so 
brittle  that  it  will  sometimes  break  with  a  single 
blow  of  the  hammer,  or  by  a  sudden  jerk,  which 
makes  it  unfit  for  axletrees,  and  other  kinds  oi"  work 
where  life  and  property  are  dependent  upon  it ;  but 
for  some  kinds  of  work  that  are  to  be  exposed  to  the 
weather  it  is  very  useful,  as  it  will  resist  the  action 
of  the  atmosphere  better  than  the  other  kinds  of 
forged  iron,  or,  in  other  words,  it  is  less  liable  to 
rust ;  it  may  generally  be  distinguished  by  a  texture 
consisting  of  large  shining  plates  without  any  fibres. 
This  kind  of  iron  is  generally  called  _cjold_jhortjr2n. 
A  fourth  kind  of  iron  (called  hot  short,  or  red  short) 
is  extremely  brittle  when 'hot,  and  malleable  when 
cold.  This  kind  of  iron  at  a  red  heat  will  hardly 
bear  to  be  turned  over  the  beak-iron  of  the  anvil 
into  the  shape  of  a  ring,  or  collar,  without  breaking, 
neither  will  a  small  rod  at  the  same  heat  stand  to  have 
a  hole  pierced  through  it  without  splitting,  and  it  is 
never  used  for  superior  kinds  of  work,  for  a  defective 
forging  is  sure  to  be  the  result  if  it  is  used  ;  but 
owing  to  its  being  much  cheaper  than  the  superior 
kinds,  and  being  very  tough  and  ductile  in  its  cold 


24  MAJSrUFACTUEE   OF   IRON. 

v  state,  for  many  purposes  it  is  a  very  useful  iron. 
On  the  surface  and  edges  of  the  bars  of  this  kind  of 
iron,  cracks  or  fissures  may  be  seen ;  and  its  internal 
appearance  is  earthy,  dull,  and  dark.  The  cause  of 
the  brittleness  in  these  last  two  kinds  of  iron  is  sup- 
posed by  some  to  be  the  presence  of  sulphur  and 
phosphorus  in  the  iron.  The  young  inquiring  mind 
may  be,  perhaps,  inclined  to  inquire,  How  does 
sulphur  and  phosphorus  get  in  the  iron  ?  The  ans  we  r 
is,  these  impurities  are  frequently  combined  more 
or  less  with  the  iron  ores,  and  in  the  roasting  process 
they  may  not  have  been  properly  got  rid  of ;  or  the 
iron  may  have  absorbed  these  impurities  from  the 
fuel  in  the  smelting  furnace,  and  the  subsequent 
processes  of  manufacture  may  not  have  properly 
purified  the  iron  ;  but  it  is  quite  probable  that  there 
are  other  accidental  causes  which  have  the  effect  of 
rendering  the  iron  brittle.  There  is  no  great  diffi- 
culty in  proving  sulphur  to  be  injurious  to  iron ; 
for,  if  a  roll  of  sulphur  (commonly  called  brimstone) 
be  held  in  one  hand,  and  a  piece  of  white  hot  iron 
be  pressed  against  it  with  the  other  hand,  the 
two  bodies  combine  and  drop  down  together  in  a 
fluid  state,  and  form  a  brittle  compound,  which  is 
neither  ductile  nor  malleable.  It  is  an  indisputable 
fact,  and  well  known  to  any  practical  man  working 
at  the  welding  of  iron,  that  sulphur  is  injurious  to 
the  iron  ;  for,  if  sulphur  be  present  in  the  fire,  the 
iron  will  not  weld. 


CHAPTEE  II. 
MANUFACTURE  OF  STEEL. 

STEEL  is  a  compound  of  iron  and  carbon,  some- 
times formed  from  wrought  iron  by  heating  the 
'wrought  iron  in  contact  with  carbon,  and  some- 
times formed  from  cast  iron  by  depriving  the  cast 
iron  of  ail  impurities  except  a  small  portion  of 
carbon.  The  proportions  of  iron  and  carbon  vary 
in  the  different  qualities  of  steel ;  but  in  that  used 
ordinarily,  the  carbon  rarely  exceeds  two  per  cent. ; 
for  some  purposes  it  is  as  low  as  one  per  cent. 
Good  ordinary  tool  steel  contains  about  one  and  a 
half  per  cent,  of  carbon.  Different  kinds  of  iron 
produce  steel  of  different  characters,  and  differ- 
ent qualities  of  steel  are  used  for  different  pur- 
poses. 

In  this  country  the  most  common  mode  of  man- 
ufacturing steel  is  by  a  process  called  cementation. 
,Mr.  Bessemer  has,  of  late  years,  however,  intro- 
duced an  entirely  new  system  of  manufacturing 
steel.  By  his  process  steel  can  be  manufactured  of 
any  degree  of  hardness  direct  from  the  cast  iron, 
without  the  intermediate  operation  of  rendering  it 
malleable,  or,  in  other  words,  without  the  interme- 
diate operation  of  puddling,  etc.  The  principle  of 
the  process  consists  in  directing  a  blast  of  cold  air 
2 


26  MANUFACTURE   OF   STEEL. 

upon  molten  cast  iron,  the  cold  air  ignites  the  car- 
bon contained  in  the  cast  iron,  and  causes  an  intense 
combustion,  and  the  carbon  is  consumed ;  and  by 
this  means  the  cast  iron  is  decarbonized  to  the  state 
of  good  tool  steel,  or  to  mild  welding  steel,  or  to 
the  state  of  malleable  iron,  according  to  the  length 
of  time  the  combustion  is  continued.  As  carbon 
has  a  strong  affinity  for  oxygen,  and  cast  iron  con- 
taining more  carbon  than  steel,  and  steel  being  a 
compound  of  iron  and  carbon,  it  will  be  seen  read- 
ily that  if  all  the  impurities  of  the  cast  iron  can  be 
got  rid  of,  and  the  process  of  combustion  can  be 
stopped  when  the  metal  is  decarbonized  to  about 
one  or  one  and  a  half  per  cent.,  good  steel  must  be 
the  product.  Mr.  Bessemer  can  manufacture  steel, 
of  any  degree  of  hardness,  by  continuing  the  pro- 
cess of  combustion  until  the  whole  of  the  carbon  is 
consumed,  and  then  adding  the  required  quantity 
of  carbon  to  form  steel  by  a  subsequent  opera- 
tion. 

Mild  cast  steel,  or  welding  cast  steel,  as  it  con- 
tains a  smaller  proportion  of  carbon  than  ordinary 
cast  steel,  is  being  more  and  more  used,  and  is  grad- 
ually superseding  the  use  of  cast  and  wrought  iron ; 
and  tjiere  is  good  reason  to  believe  that  steel  of  ex- 
cellent quality,  for  numerous  purposes,  will,  at  no 
distant  period,  be  manufactured  cheaper  than 
wrought  iron  is  now  produced  by  the  operation 
of  puddling. 

The  furnace  in  which  iron  is  cemented  and  con- 
verted into  steel,  called  a  converting  furnace,  has 
the  form  of  a  large  oven,  constructed  so  as  to  form 


MANUFACTURE   OF   STEEL.  27 

in  the  interior  of  the  oven  two  large  and  long  cases, 
commonly  called  troughs  or  pots,  and  built  of  good 
fire-stone  or  fire-brick.  Into  each  of  these  pots 
layers  of  the  purest  malleable  iron  bars,  and  layers 
of  powdered  charcoal,  are  packed  horizontally  one 
upon  the  other  to  a  proper  height  and  quantity 
according  to  the  size  of  the  pots,  leaving  room  every 
way  in  the  pots  for  the  expansion  of  the  metal  when 
it  becomes  heated.  The  bars  are  cut  to  certain 
lengths,  ten,  twelve,  or  more  feet,  according  to  the 
lengths  of  the  pots.  A  hole  is  left  in  the  end  of 
one  of  the  pots,  and  three  or  four  bars  are  placed 
in  such  a  manner  that  they  can  be  drawn  out  at 
any  period  of  the  process  and  examined.  After  the 
packing  of  the  pots  is  completed  the  tops  are  cov- 
ered with  a  bed  of  sand  or  clay.  This  is  to  confine, 
the  carbon  and  exclude  the  atmospheric  air.  All 
the  open  spaces  of  the  furnace  are  then  closed,  the 
fire  is  kindled,  and  the  flame  passes  between,  under, 
and  around  these  pots  on  every  side,  and  the  whole 
is  raised  to  a  considerable  intensity  of  heat.  This 
heat  is  kept  up  for  eight  or  ten  days,  according  to 
the  cfegree  of  hardness  required.  On  the  fifth  or 
sixth  day  a  test  bar  is  drawn  out  of  the  converting 
pot  for  the  purpose  of  judging  whether  the  iron  is 
at  its  proper  heat,  and  to  test  the  progress  of  the 
carbonization.  At  this  period  of  the  process  the 
film  of  iron  is  generally  distinguished  in  the  centre 
of  the  bar,  and  the  fire  is  generally  kept  up  for  a 
day  or  two  longer  in  order  that  the  iron  may  absorb 
more  carbon.  If,  again,  upon  the  trial  of  a  bar,  the 
cementation  has  extended  to  the  centre,  or,  in  other 


28  MANUFACTURE   OF   STEEL. 

words,  if  the  bars  of  iron  have  absorbed  the  car- 
bonaceous principle  to  their  innermost  centre,  the 
whole  substance  is  converted  into  steel,  and  the 
work  is  complete.  The  fire  is  withdrawn  or  extin- 
guished by  closing  the  vents,  and  the  mass  is  left 
to  cool  for  several  days.  The  furnace  may  contain, 
according  to  its  size,  from  ten  to  thirty  tons  of  iron 
at  each  charge,  and  the  whole  process  occupies 
fourteen  or  fifteen  days. 

By  this  process,  carbon,  probably  in  the  state 
of  vapor,  penetrates  and  combines  with  the  iron, 
which  is  thus  converted  into  steel.  The  properties 
of  steel  being  influenced  by  the  properties  of  the 
iron  from  which  it  is  manufactured,  those  only  who 
possess  a  knowledge  of  the  properties  of  the  iron 
used  are  enabled  to  prepare  steel  fitted  for  any  re- 
quired purpose. 

The  properties  of  iron  are  remarkably  changed 
by  cementation,  and  it  acquires  a  small  addition  to 
its  weight,  in  proportion  to  the  carbon  it  has  ab- 
sorbed from  the  charcoal.  It  is  much  more  brittle 
and  fusible  than  before,  and  loses  much  of  its  duc- 
tility and  malleability,  but  gains  in  hardness,  and 
elasticity,  and  sonorousness.  The  texture,  which 
was  originally  fibrous,  has  by  the  process  become 
granular ;  and  its  surface  acquires  a  blistered  char- 
acter, and  presents,  when  broken,  a  fracture  much 
like  inferior  iron. 

The  continuance  of  the  process  of  cementation 
introduces  more  and  more  carbon  ;  and,  if  the  ce- 
mentation be  continued  too  long,  or,  if  the  heat  be 
too  intense,  the  steel  becomes  porous,  more  brittle 


MANUFACTURE   OF   STEEL.  29 

and  more  fusible,  in  which  state  it  is  more  difficult 
to  weld ;  but,  if  it  has  not  been  over-cemented,  it 
retains  the  property  of  welding,  and  may  be  welded 
either  to  itself  or  to  iron.  But  the  most  impor- 
tant alteration  in  its  properties  is,  that  it  can  be 
hardened  by  heating  it  to  a  bright-red  heat,  and 
suddenly  quenching  it  in  cold  water,  which  is  a 
property  it  did  not  possess  when  in  the  state  of 
pure  malleable  iron ;  and  it  is  to  its  carbon  that 
it  owes  this  most  valuable  property.  By  the 
application  of  heat,  hardened  steel  may  be  softened 
down  again  to  any  requisite  degree.  The  process 
of  reducing  the  hardness  of  steel  is  called  tem- 
pering. 

It  may  be  well  to  state,  that  some  kinds  of  mal- 
leable iron  may  also  be  hardened  in  a  small  degree 
by  heating  to  a  red  heat  and  suddenly  quenching1 
in  cold  water ;  but  the  effect  is  confined  to  the  sur- 
face, except,  as  it  very  often  happens,  that  the  iron 
contains  veins  of  steel.  Pure  malleable  iron,  how- 
ever, does  not  possess  hardening  properties ;  it 
should  be  equally  soft,  whether  suddenly  or  slowly 
cooled.  Although  pure  malleable  iron  does  not 
possess  hardening  properties,  still,  it  is  rendered 
more  rigid  by  being  suddenly  cooled.  This  effect 
is  owing  to  the  compression  of  the  particles  into  a 
denser  state ;  and,  for  some  purposes  where  stiff- 
ness combined  with  a  certain  amount  of  flexibility 
is  required,  small  lumps  of  pure  malleable  iron  are 
the  better  for  being  immersed  in  water. 

The  contractile  forces  of  large  lumps  of  malle- 
able iron  when  plunged  into  water  will  induce 


30  MANUFACTURE   OF   STEEL. 

strains,  which  have  a  tendency  to  rend  open  the 
interior  of  the  mass.  The  water  acting  suddenly 
upon  the  surface  causes  the  compression  to  be  too 
sudden,  consequently  it  would  be  disadvantageous 
to  immerse  a  large  mass  of  pure  malleable  iron  in 
cold  water.  "When  a  lump  of  pure  malleable  iron 
is  required  more  rigid  than  when  in  its  natural 
state,  and  less  rigid  than  when  immersed  in  cold 
water,  it  may  be  heated  to  a  bright-red  heat  and 
cooled  in  oil.  The  oil  acting  less  suddenly  than 
water  upon  the  iron,  it  is  obvious  that  an  internal 
fracture  is  less  likely  to  occur. 

Iron  prepared  by  the  process  previously  men- 
tioned is  called  blistered  steel,  from  the  blisters 
which  appear  on  its  surface,  the  blisters  being 
caused  by  the  long  continuance  of  heat,  and  proba- 
bly the  expansion  of  air  within  these  blisters. 
When  the  bars  of  blistered  steel  are  heated  and 
drawn  out  into  smaller  bars  by  means  of  the  ham- 
mer, it  acquires  the  name  of  tilted  steel.  Spring 
steel  is  the  blister  steel,  simply  heated  and  rolled, 
but  frequently  the  iron  is  specially  cemented  for 
spring  steel ;  by  the  compression  and  elongation 
of  its  particles  under  the  hammer,  or  between  the 
rollers,  the  material  is  improved  increasingly  in  a 
remarkable  degree. 

Shear  steel  is  produced  by  cutting  the  bars  of 
blistered  steel  into  convenient  lengths,  and  piling 
and  welding  them  together  by  means  of  a  steam- 
hammer.  Striking  in  rapid  succession  upon  the 
steel,  it  closes  the  seams  and  removes  the  blisters. 
By  this  rapid  hammering  the  steel  is  kept  in  better 


MANUFACTURE   OF   STEEL.  31 

temper,  and  fewer  heats  are  required  for  the  same 
work.  The  bars,  after  being  welded  and  drawn 
out,  are  again  cut  to  convenient  lengths,  piled  and 
welded,  and  again  drawn  out  into  bars.  It  is  then 
called  double  shear  steel ;  hence  the  name  single 
or  double  shear  steel,  according  to  the  extent  of  the 
process  of  conversion.  The  bars  are  then  ready  for 
forging  or  rolling,  according  to  the  purposes  for 
which  it  is  designed.  Shear  steel  breaks  with  a 
finer  fracture,  is  tougher,  and  capable  of  receiving 
a  finer  and  firmer  edge  and  a  higher  polish  than 
blistered  or  spring  steel ;  and,  when  well  prepared, 
it  is  not  much  inferior  to  cast  steel.  Shear  stepl  is 
very  extensively  used  for  those  kinds  of  tools  and 
pieces  of  work  composed  of  steel  and  iron. 

Steel  of  cementation,  however  carefully  made, 
is  never  quite  equable  in  its  texture,  but  the  tex- « 
ture  of  steel  is  rendered  more  uniform  by  fusion ; 
when  it  has  undergone  this  operation  it  is  cast 
steel.  The  best  cast  steel  is  produced  by  the  inven- 
tion of  Mr.  Benjamin  Huntsman,  of  Sheffield^  long 
since  deceased.  It  is  nearly  a  hundred  years  since 
it  was  first  invented,  but  the  process  still  remains 
in  principle  unaltered.  Cast  steel  is  made  from 
fragments  of  the  blister  steel  of  the  steel- works. 
The  process  adopted  is  that  of  taking  the  blister 
steel,  converted  to  a  certain  degree  of  hardness, 
and  breaking  it  into  pieces  of  convenient  length, 
and  weighing  about  a  pound  each ;  small  crucibles, 
made  of  the  most  refractory  fire-clay,  which  are 
capable  of  holding  about  thirty  pounds  or  more  in 
weight,  are  then  charged  with  these  fragments,  and 


32  MANUFACTURE   OF   STEEL. 

placed  in  furnaces  similar  to  those  used  in  brass- 
founderies.  The  furnaces  are  furnished  with  covers 
and  chimney  to  increase  the  draught  of  air,  and  the 
crucibles  are  furnished  with  lids  of  clay  to  exclude 
the  atmospheric  air.  The  furnaces  containing  the 
crucibles  are  filled  with  coke ;  and,  for  the  perfect 
fusion  of  the  steel,  the  most  intense  heat  is  kept  up 
for  two  or  three  hours.  When  the  steel  is  thoroughly 
melted,  the  melter,  with  a  long  pair  of  tongs,  draws 
out  of  the  fire  the  crucibles,  and  pours  the  contents 
in  its  then  liquid  state  into  ingot-moulds  of  the 
shape  and  size  required.  Although  steel  may  be 
cast  into  ingots,  it  is  too  imperfectly  fluid  to  be  cast 
into  very  small  articles.  The  crucibles,  directly 
they  are  emptied,  if  they  are  sound,  are  returned 
into  the  furnace  and  again  charged.  The  ingots 
of  steel,  once  crude  iron,  but  now  changed  by 
chemical  action  into  cast  steel,  are  taken  to  the 
forge  or  rolling-mill,  and  afterward  prepared  for 
the  market  by  hammering  or  rolling  into  bars 
or  plates,  as  may  be  required,  in  the  same  manner 
as  other  steel,  but  with  less  heat  and  with  more 
precaution ;  for  the  finest  cast  steel  melts  at  a  lower 
heat  than  any  other  steel,  and  is,  therefore,  more 
readily  degraded  in  the  fire,  and  is  dispersed  under 
the  hammer  or  between  the  rollers,  if  heated  to  a 
white  heat.  Cast  steel  is  the  most  uniform  in  qual- 
ity, the  hardest  and  the  most  reliable  steel  for  cut- 
ting tools,  especially  for  those  made  entirely  of  steel ; 
and  it  is  used  for  all  the  finest  cutlery.  Cast  steel 
is  dearer  than  the  other  kinds  of  steel,  owing  prin- 
cipally to  the  large  quantity  of  fuel  employed  for 


MANUFACTURE   OF   STEEL.  33 

its  fusion.  Its  uniformity  of  texture  enables  it  to 
take  a  fine,  firm  edge,  and  receive  the  exquisite 
polish  of  which  no  other  steel  is  in  so  high  a  degree 
susceptible ;  and  its  unrivalled  superiority  is  ac- 
knowledged in  all  parts  of  the  globe. 


CHAPTER  III. 
CHOOSING    OF    STEEL. 

IT  would  be  far  easier  for  me  to  choose  good  from 
bad  tool  steel  than  to  describe  how  to  choose  it. 
However,  it  may  be  well  to  state  that,  in  choosing 
steel  for  cutting-tools,  where  tenacity  as  well  as 
hardness  is  required,  some  technical  knowledge  is 
requisite ;  although  the  differences  of  steel  consist 
in  its  composition,  it  is  not  always  necessary  to  sub- 
ject it  to  chemical  analysis  in  order  to  know  its 
nature  or  character.  The  hardness  and  tenacity  of 
steel,  and  the  other  properties  of  forging  and  weld- 
ing, are  very  useful  in  distinguishing  its  qualities  ; 
but  it  is  also  necessary  to  ascertain  these  properties 
with  precision.  Marks  or  signs,  by  which  to  know 
by  sight,  by  sound,  or  by  strength,  good  tool  steel, 
are  doubtless  fallacious.  Sight  may  afford  some- 
times an  idea  of  the  quality  of  steel,  but  it  cannot 
be  depended  upon  ;  even  with  great  experience  the 
result  is  always  uncertain.  The  usual  method  of 
choosing  steel  for  tools,  Which  require  a  fine,  firm 
edge,  is  to  break  a  bar,  and  to  observe  its  fracture 
and  select  that  which  has  a  moderately  fine  grain  ; 
but  this  method  is  not  always  certain,  as  a  variation 
in  the  fracture  will  be  caused  by  the  hardness  or 
softness  of  the  steel,  or,  in  other  words,  by  the  dif- 


CHOOSING   OF   STEEL.  35 

ference  of  its  temper,  and  the  greater  or  less  heat 
at  which  it  has  been  hammered  or  rolled,  and  some 
steel  breaks  of  a  very  close  grain,  though  of  very 
indifferent  quality.  Several  methods  may  be  prac- 
tised to  ascertain  the  goodness  of  the  steel,  but  if 
there  is  an  opportunity  of  forging  some  of  the  steel, 
it  is  advisable  to  do  so  ;  for,  in  my  opinion,  there  is 
no  better  means  of  ascertaining  its  true  character. 
In  the  first  place  it  will  be  requisite  to  ascertain  the 
highest  degree  of  heat  the  steel  will  bear  without 
injury,  and  then  to  keep  always  a  little  below  this 
heat.  Steel  will  not  bear  the  same  degree  of  heat, 
without  injury,  as  iron;  and  steel  which  will  not 
bear  a  high  heat  in  forging  will  not  bear  a  high 
heat  in  hardening.  Blistered  steel  will  resist  a  far 
higher  degree  of  heat  than  highly  carbonized  cast 
steel,  and  good  shear  steel  will  endure  a  white  flamfe 
heat  without  much  injury;  also  a  welding  heat,  if 
subsequently  hammered.  Although  iron  will  bear 
a  higher  degree  of  heat  than  steel,  yet  steel  will 
bear  a  far  greater  amount  of  hardship  under  the 
hammer  than  iron — that  is,  if  the  steel  is  cautiously 
heated.  Good  cast  steel,  which  is  suitable  for  the 
best  kinds  of  cutting-tools  which  have  to  "endure  a 
great  amount  of  hard  work,  will  not  bear  a  white 
heat  without  falling  to  pieces ;  it  will  hardly  sustain 
a  bright-red  heat  without  crumbling  under  the 
hammer,  but  at  a  middling  or  cherry-red  heat  it 
will  bear  drawing  under  the  hammer  to  a  point  as 
fine  as  a  needle.  Inferior  steel,  whether  at  a  high 
or  low  heat,  will  not  take  such  a  fine  point  without 
splitting ;  and  steel  which  will  not  take  a  fine  point 


36  CHOOSING  OF   STEEL. 

will  not  receive  a  fine,  firm  edge,  however  skilfully 
the  hardening  and  tempering  may  be  performed. 

There  are  some  kinds  of  steel  which  are  very 
tenacious,  and  which  will  take  a  moderately  fine 
sound  point,  but,  found  deficient  in  their  hardening 
properties,  must  be  rejected  for  the  best  kinds  of 
tools.  Drawing  a  piece  of  steel  to  a  point  for  test- 
ing it  is  a  simple  process ;  but,  simple  as  it  is,  without 
some  degree  of  attention  it  may  produce  false  results 
and  mislead  the  unwary.  For  instance,  suppose  we 
were  to  take  a  piece  of  steel  cut  from  a  bar,  and 
commence  to  draw  the  extreme  end  of  it  to  a  point, 
if  the  extreme  end  of  this  piece  of  steel  should  happen 
to  be  even  in  a  small  degree  concave,  previous  to 
hammering  it,  we  cannot  succeed  in  getting  a  fine 
sound  point,  although  the  steel  should  be  the  best 
Sheffield  can  furnish ;  for,  in  hammering  it,  the  sur- 
face steel  will  overrun  the  centre,  and  cause  the 
extreme  end  to  be  concave  in  a  greater  degree,  and 
so  long  as  this  concavity  exists  in  the  end  the  steel 
cannot  take  a  fine  sound  point.  To  avoid  this,  pre- 
vious to  commencing  to  draw  the  steel  to  a  point, 
the  extreme  end  of  the  piece  of  steel  under  trial  may 
be  either  ground  or  filed  to  a  rounded  point  similar 
to  a  centre  punch  but  not  quite  so  sharp ;  and,  if  the 
steel  is  tenacious,  we  will  then  succeed  in  drawing  it 
to  a  fine  sound  point.  Another  method  is  to  take  a 
piece  of  steel  just  as  it  is  cut  or  broken  from  a  bar, 
without  filing  or  grinding  the  end ;  heat  one  end  of 
it  to  a  cherry-red  heat,  and  place  it  upon  the  project- 
ing arm  of  the  anvil,  called  the  beak-iron ;  the  extreme 
end  of  the  steel  must  be  allowed  to  project  over  the 


CHOOSING   OF  STEEL.  37 

beak-iron  so  as  not  to  make  use  of  it,  and  then  draw 
the  steel  to  a  gradually  tapered  square  point ;  the 
small  piece  which  was  allowed  to  project  over  the 
beak-iron  must  now  be  taken  off  by  filing  the  steel 
through  at  the  smallest  part,  after  which  it  must  be 
reheated  and  drawn  to  a  finer  point — that  is,  of 
course,  if  the  steel  will  take  a  finer  point  without 
splitting.  A  welding  heat  will  of  course  be  required 
to  test  the  welding  properties  of  steel,  but  a  welding 
heat  should  not  be  used  when  drawing  the  steel  to  a 
point  to  test  its  tenacity  under  the  hammer.  The 
extreme  end  of  a  bar  of  steel,  in  the  state  it  leaves 
the  tilt  or  the  rollers,  should  not  be  taken  for  testing 
the  quality  of  the  steel;  it  should  be  rejected  on 
account  that  it  is  looser  and  more  porous  than  the 
other  parts  of  the  bar.  For  the  sake  of  having  a 
clearer  idea  of  our  subject,  let  us  suppose  the  piece 
of  steel  to  have  received  a  fine  sound  point,  and  to 
be  possessed  of  tenacity ;  the  next  operation  will  be 
to  test  its  hardening  properties,  and  to  ascertain  the 
degree  of  its  tenacity.  Tenacity  is  an  opposite 
quality  to  brittleness ;  therefore,  if  the  hardness  is 
not  accompanied  with  a  certain  degree  of  tenacity 
the  steel  will  be  of  very  little  service  for  the  best 
kinds  of  cutting-tools  or  for  surgical  instruments ; 
therefore  it  becomes  an  object  of  importance  to  at- 
tend to  this  trial  most  carefully.  The  fine  point  of 
this  piece  of  steel  under  trial  may  now  be  cut  off, 
and  the  steel  drawn  out  again  under  a  low  heat  to 
a  gradually  tapered  square  point,  but  not  so  fine  as 
before ;  it  must  then  be  plunged  suddenly  at  this 
heat  into  pure  cold  water ;  the  hardened  point  may 


38  CHOOSING   OF   STEEL. 

then  be  tried  with  a  smooth  file,  but  I  may  state 
that  this  mode  of  trial  with  a  file  is  defective,  as 
files  differ  in  hardness  and  only  serve  to  tell  in  an 
imperfect  manner  the  hardness  of  the  steel ;  but  if 
the  point  be  broken  off  just  enough  to  show  the 
fracture,  and  it  will  easily  scratch  glass,  it  is  a 
positive  proof  that  the  steel  is  hard  and  possessed 
of  good  hardening  properties.  The  power  used  in 
breaking  affords  some  knowledge  of  the  tenacity  of 
the  steel.  The  broken  point  may  be  tried,  and  the 
degree  of  the  tenacity  of  the  steel  ascertained,  by 
placing  it  upon  a  piece  of  hard  cast  iron  and 
crushing  it  under  the  face  of  a  small  hardened 
hammer;  if  the  steel  is  good  it  will  resist  the 
crushing,  and  will  cut  the  hammer's  face,  and  bury 
itself  in  the  cast  iron.  Inferior  steel,  having  little 
or  no  tenacity,  by  this  test  will  be  ground  to  powder 
or  crushed  flat,  nearly  as  easily  as  a  piece  of  hard 
iron,  and  will  not  enter  the  cast  iron.  The  degree 
of  resistance  of  this  grain  of  steel  to  the  crushing 
power  is  a  good  rule  by  which  to  judge  of  it,  for 
many  kinds  of  steel  feel  hard  to  the  file  and  yet  show 
no  tenacity.  If  the  steel  under  trial  will  take  a  fine 
sound  point,  and  after  plunging  it  when  red  hot  into 
pure  cold  water  require  a  moderate  force  to  break 
it,  prove  hard  and  will  easily  scratch  glass  and  resist 
the  crushing  power,  whatever  its  fracture  may  be  it 
is  good.  The  excellence  of  steel  will  always  be  in 
proportion  to  the  degree  of  its  tenacity  in  its  hard 
state. 

Another  mode  of  trial,  more  simple  and  more 
economical,  and  less  delicate  than  the  former,  and 


CHOOSING   OF   STEEL.  39 

on  the  results  of  which  full  reliance  may  be  placed, 
is  carefully  to  forge  a  flat  and  a  diamond-pointed 
chipping-chisel,  which  must  be  carefully  hardened 
and  afterward  tempered  to  a  violet  color,  after 
which  to  be  ground  upon  the  grinding-stone,  and 
then  tested  upon  a  piece  of  hard  cast  iron.  If  the 
chisels  resist  the  blows  of  the  hammer  without  break- 
ing, and  keep  a  sharp,  firm  edge,  full  reliance  may 
be  placed  on  the  quality  of  the  steel ;  for  in  my 
opinion  there  is  nothing  which  will  indicate  the 
quality  of  the  steel  better  than  a  diamond-pointed 
chisel  tested  upon  a  piece  of  hard  cast  iron ;  for  it 
supplies  us  precisely  with  the  information  we  are 
seeking,  namely,  whether  hardness  and  tenacity  are 
combined  in  the  steel.  If  the  chisels  prove  good 
there  is  no  waste  of  steel,  for  the  result  of  the  test  is 
two  good  and  useful  tools.  If  the  steel  does  not 
prove  satisfactory,  the  chisels  need  not  be  wasted, 
for  they  may  be  easily  altered  into  either  round, 
square,  or  flat  punches  for  piercing  hot  iron ;  for  the 
steel  would  be  very  bad  indeed  if  it  would  not  do 
for  this  purpose — so  bad,  that  it  could  l^e  readily 
detected  by  the  eye  in  the  first  instance  when  the 
bar  was  broken.  In  general,  in  its  soft  state,  a  curved- 
line  fracture  and  uniform  gray  texture  denotes 
good  steel ;  and  the  appearance  of  threads,  cracks, 
or  sparkling  particles  is  a  proof  of  the  contrary. 

Good  tool  steel  in  its  hard  state  on  fracture  pre- 
sents a  dull  silvery  appearance,  is  more  close  in  its 
texture  than  annealed  steel,  and  is  of  a  uniformly 
white  color,  with  the  entire  absence  of  sparkling 
particles.  If  aquafortis  be  applied  to  the  surface 


40  CHOOSING   OF   STEEL. 

of  steel  previously  brightened,  it  immediately  pro- 
duces a  black  spot ;  but  if  applied  to  iron  the  metal 
remains  clean,  so  that  it  will  be  quite  easy  to  select 
such  pieces  of  iron  or  steel  which  possess  the  great- 
est degree  of  uniformity,  as  the  smallest  vein,  either 
of  iron  or  steel,  upon  the  surface,  will  be  distinguished 
by  its  peculiar  sign. 


CHAPTER  IV. 
FORGING  AND  WELDING  IKON  AND  STEEL. 

THE  forge,  furnished  with  furnaces,  steam-ham- 
mers, cranes,  anvils,  swage-blocks,  and  various  other 
kinds  of  tools,  is  the  workshop  in  which  iron  and 
steel  are  welded  and  fashioned  with  the  hammer. 
Welding  is  that  operation  by  which  pieces  of  iron 
or  steel,  or  steel  and  iron,  are  equally  heated  nearly 
to  a  state  of  fusion  arid  appear  to  be  covered  with 
a  strong  glaze  or  varnish,  are  brought  together  and 
united  by  repeated  blows  of  the  hammer  or  under 
pressure,  and  the  union  not  to  be  perceived. 

The  heat  the  iron  receives  in  forging  is  judged 
by  the  eye,  and  is  not  commonly  distinguished  into 
more  than  these  five  degrees,  namely,  the  dark-red 
heat,  the  blood  or  low  cherry-red  heat,  the  bright 
cherry-red  heat,  the  white-flame  heat,  and  the  spark- 
ling or  welding  heat. 

The  dark-red  heat  is  not  visible  in  daylight,  but 
shines  in  the  dark  with  a  brown  color,  and  is  used 
only  when  stiffness  and  elasticity  are  required. 

The  blood  or  low  cherry-red  heat  is  used  to  give  a 
fine  polish  or  skin  to  the  iron. 

The  bright  cherry-red  heat  gives  the  thin  scale  or 
oxide  on  the  iron  a  black  appearance ;  and  forgings 


42        FOKGING  AND   WELDING  IRON   AND   STEEL. 

of  any  description  ought  to  be  smoothed  and  finished 
at  this  heat. 

The  white-flame  heat  is  that  which  gives  the 
scales  and  the  iron  the  same  color,  and  is  used  for 
forging,  or  changing  the  form,  of  iron  when  weld- 
ing is  not  required. 

The  sparkling  or  welding  heat  is  that  which 
gives  the  iron  the  appearance  of  being  covered  with 
a  glaze  of  varnish,  and  is  used  for  uniting  two  or 
more  pieces  of  iron  together,  or  a  multiplicity  of 
pieces  into  a  solid  mass. 

The  heat  required  for  welding  iron  varies  in  some 
degree  with  the  purity  of  the  iron.  Pure  fibrous 
iron  will  bear  almost  any  degree  of  heat  without 
much  injury,  if  not  too  long  exposed  to  the  heat ; 
while  impure  iron  bears  but  a  moderate  degree  of 
heat  without  being  melted  or  burnt. 

Although  iron  requires  to  be  heated  nearly  to  a 
state  of  fusion  before  it  can  be  welded  (at  least  when 
heat  alone  is  applied),  still  care  must  be  taken  to 
prevent  the  iron  from  running,  or  it  will  make  it  so 
brittle  as  to  prevent  its  forging,  and  sometimes  so 
hard  as  to  resist  the  cutting-tool,  or  the  file.  This 
accident  will  sometimes  occur  with  the  most  skil- 
ful workman  ;  and,  when  it  does  occur,  the  whole 
of  the  iron  which  is  injured  by  the  extreme  heat 
should  be  cut  off  and  rejected.  If  it  cannot  con- 
veniently be  cut  off,  the  whole  of  the  forging  ought 
to  be  rejected,  more  especially  if  life  or  property  is 
depending  upon  it. 

The  ordinary  fuel  used  for  the  forging  of  iron  in 
this  country  is  coal ;  and,  from  its  abundance  and 


FOKGING   AND   WELDING   EBON   AND   STEEL.         43 

cheapness,  it  is  more  frequently  used  in  forging 
steel  than  either  coke  or  charcoal.  Charcoal,  on  ac- 
count of  its  purity  compared  with  other  kinds  of 
fuel,  is  undoubtedly  the  best  fuel  that  can  be  used 
for  the  heating  of  steel ;  but,  owing  to  the  scarcity 
of  wood  in  this  country,  which  makes  it  so  expensive, 
it  is  seldom  used.  Coke,  cinders,  and  turf  are  the 
next  best  kinds  of  fuel  for  heating  steel.  Dry  coal- 
dust  is  injurious  to  steel. 

The  heaviest  works  or  forgings  are  generally 
heated  in  air  furnaces  ;  and  the  heavy  iron  forgings 
are  usually  made  up  of  scrap  iron.  The  scrap  iron 
is- cut  up  into  small  pieces  by  the  shears  ;  it  is  then 
piled  or  fagoted  into  convenient-sized  masses  of 
one  or  two  hundred  weight,  and  placed  in  the  fur- 
nace. The  fire  is  urged,  and  the  mass  is  raised  to 
the  welding  heat ;  it  is  then  withdrawn,  and  placed 
under  the  hammer,  and  united  into  a  bloom  or  slab. 

Blooms  and  slabs  are  sometimes  made  of  the 
shavings  that  are  cut  from  the  iron  at  the  turning 
or  boring  lathes.  From  one  to  two  hundred  weight 
of  the  shavings  are  thrown  into  the  furnace,  and 
spread  evenly  over  the  bottom ;  the  fire  is  urged, 
and  the  workman  observes  through  a  small  hole  in 
the  furnace-door  provided  for  the  purpose,  and  for 
the  introduction  of  his  tools,  the  progress  of  the 
heat.  As  soon  as  the  iron  arrives  at  the  welding 
temperature,  the  workman  collects  it,  and  makes 
it  up  by  means  of  his  tools  (a  rod  of  iron  with  an 
eye  at  one  end,  and  a  hook  at  the  other),  and 
while  it  is  yet  in  the  furnace,  into  a  spherical 
form ;  he  then  rolls  it  about  in  the  furnace,  so  as  to 


44:        FOEGING   AND  WELDING  IEON  AND   STEEL. 

insure  an  equable  temperature  to  the  mass,  after 
which  the  furnace-door  is  lifted,  and  the  ball  remov- 
ed from  the  furnace  by  means  of  a  hand-truck ;  the 
workman  then  grips  it  with  a  pair  of  tongs,  and 
shingles  it  under  a  heavy  hammer  into  a  square  or 
oblong  bloom ;  after  which  the  bloom  is  reheated  to 
the  welding  temperature,  and  subjected  to  a  second 
hammering,  in  order  to  get  rid  of  all  the  dirt,  or 
scoria,  which  may  have  got  closed  up  with  the  iron. 
In  order  to  make  it  more  compact,  and  more  thor- 
oughly to  condense  the  particles,  it  is  then  hammer- 
ed into  the  form  of  a  flat  slab.  Several  of  these 
slabs  heated,  and  welded  together,  form  the  masses 
of  which  large  forgings  are  generally  built  up. 

When  a  mass  is  too  large' to  be  handled  conve- 
niently by  the  forgeman  with  the  tongs,  a  large  iron 
rod  is  welded  to  it,  to  serve  as  a  porter  or  guide-rod, 
and  the  welding  of  the  rod  to  the  mass  is  performed 
in  a  variety  of  ways.  The  end  of  the  rod  is  sometimes 
inserted  into  the  mass  within  the  furnace ;  and, 
when  the  whole  is  at  the  welding  temperature,  the 
other  end  of  the  rod  is  struck  with  the  sledge-hammer, 
which  welds  it  sufficiently  to  lift  the  mass  from  the 
furnace  to  the  hammer.  Sometimes  the  end  of  the 
rod  is  heated  in  a  separate  part  of  the  furnace,  and 
made  to  arrive  at  the  welding  temperature  at  the 
same  time  as  the  mass ;  and,  when  the  mass  is  with- 
drawn from  the  furnace,  the  rod  is  withdrawn  also, 
and  generally  welded  on  by  the  first  blow  of  the 
hammer.  Sometimes  a  part  of  the  porter-bar  is 
made  to  form  the  core  of  the  forgings,  and  the  slabs 
or  masses  of  iron  which  form  the  forgings  are  welded 


FOKGING  AND   WELDING-  IEON   AND   STEEL.         45 

and  built  upon  the  bar.  When  a  mass  of  irou  or 
forging  is  too  large  to  be  handled  bj  the  forgeman 
with  the  porter  or  guide-rod,  it  is  supported  by  a 
crane,  which  serves  to  swing  it  from  the  fire  to  the 
hammer ;  likewise  it  serves  for  the  different  changes 
of  elevation  which  the  work  at  times  requires ;  it 
serves  also  for  moving  the  work  to  and  fro  upon  the 
anvil.  A  cross  lever  is  temporarily  fixed  to  the 
porter,  the  use  of  which  is  to  enable  the  workmen  to 
turn  the  work  over  so  as  to  expose  all  the  parts  to 
the  action  of  the  hammer,  when  it  is  manipulated 
wmi  the  greatest  ease ;  and  the  mere  sight  of  the 
welding  and  manipulation  of  large  masses  of  iron, 
when  conducted  by  a  skilful  workman,  is  always 
interesting,  even  when  of  every-day  occurrence. 

The  mingling  of  the  fibres  in  the  scrap  iron  is 
generally  considered  highly  favorable  to  the  strength 
of  the  forging,  which  probably  it  is  when  the  scrap 
iron  is  of  good  quality  ;  but  scrap  iron  of  an  inferior 
quality,  or  a  mixture  of  all  qualities  (however  skil- 
fully the  operation  of  forging  and  welding  may  be 
performed),  can  never  produce  a  forging  so  good  as 
new  bar  iron  of  good  quality,  cut  up  into  lengths, 
piled,  and  welded. 

The  mingling  of  the  good  iron  with  the  bad  iron 
probably  does  have  the  effect  of  improving  the  bad 
iron ;  but  the  bad  iron  cannot  have  the  effect  of  im- 
proving the  good  iron.  But  it  may  be  said  that  the 
hammering  has  the  effect  of  improving  the  bad  iron, 
and  without  a  doubt  it  does  do  so  to  a  certain  degree ; 
and,  if  hammering  improves  bad  iron,  it  must  cer- 
tainly improve  good  iron  to  a  certain  degree  also, 


46        FOKGING  AND  WELDING  IKON  AND   STEEL. 

thus  showing  that  new  bar  iron  of  good  quality  must 
certainly  produce  a  better  forging  than  scrap  iron  of 
bad  quality,  or  scrap  iron  of  all  qualities ;  for  the 
forging  must  certainly  be  more  uniform  in  metal,  and 
more  uniform  in  temper,  consequently  it  must  be 
more  uniform  in  elasticity  and  tenacity.  The  quality 
of  iron  is  much  improved  by  violent  compression, 
such  as  by  forging  and  rolling.  It  gives  much  greater 
strength  to  the  iron,  by  its  being  elongated  and  solid- 
ified, especially  when  it  is  not  long  exposed  to  vio- 
lent heat ;  but  when  it  is  long  exposed  to  violet 
heat,  its  particles  undergo  an  injurious  change  of 
position,  and  the  heat  at  length  destroys  its  metallic 
properties ;  but,  though  iron  is  rendered  malleable 
by  hammering,  still  this  operation  may  be  continued 
so  long  as  to  deprive  it  of  its  malleability,  also  its 
fibrous  character ;  and  the  more  readily  with  the 
absence  of  a  sufficient  degree  of  heat. 

When  a  large  solid  forging  is  required  perfectly 
sound  throughout  the  mass,  and  which  is  made  up 
either  with  scrap  or  new  bar  iron,  there  is  no  better 
method  than  to  forge  it  square ;  that  is,  with  four 
flat  sides.  This  plan  is  seldom  adopted  with  a  for- 
ging which  is  required  round,  on  account  of  a  greater 
amount  of  time  being  required  to  turn  it  in  the  turn- 
ing-lathe. Though  this  method  is  seldom  adopted, 
it  does  not  make  it  any  the  less  effective  in  produ- 
cing the  soundest  forging ;  as  it  must  be  evident  to 
those  who  have  ever  thought  at  all  upon  the  subject, 
that  large  forgings,  which  are  hammered  or  forged 
round  upon  fiat  surfaces,  or  between  the  half  circle 
swage-tools,  or  even  between  the  Y  swage-tools,  can 


FORGING   AND   WELDING   IKON   AND   STEEL.         4:7 

never  be  so  dense  and  solid  as  forgings  which  are 
forged  square  (with  four  flat  sides).  A  forging 
forged  with  six  sides  will  always  be  denser  and  more 
solid  than  a  forging  which  is  forged  round  between 
flat  surfaces  ;  but  it  will  be  less  dense,  and  less  solid, 
than  a  forging  forged  with  four  flat  sides,  for  these 
reasons,  that  the  larger  the  squares,  the  more  iron 
there  is  under  compression  at  the  same  time,  conse- 
quently the  denser  and  more  solid  the  forging  be- 
comes. Forgings  made  in  dies  are  prevented  from 
Becoming  hollow  in  the  centre ;  but,  with  very 
large  forgings,  this  method  is  quite  impracticable. 

When  a  forging  is  being  made  round  between 
flat  surfaces,  there  is  such  a  small  quantity  of  the 
whole  mass  under  compression  at  one  time,  that 
every  blow  of  the  hammer  tends  to  make  the  forging 
hollow  or  porous  in  the  centre  by  forcing  out  the 
sides  of  the  forging  at  every  successive  blow ;  the 
greater  the  force  of  the  blows,  the  greater  the  effect 
in  causing  the  forging  to  become  hollow  (commonly 
called  spongy)  at  the  centre ;  the  less  the  force  of 
the  blows,  the  greater  the  effect  in  causing  the  for- 
ging to  become  hollow  at  the  part  between  the  sur- 
face and  the  centre,  as  every  blow  of  the  hammer 
has  the  effect  of  drawing  and  enlarging  the  outer 
case  of  the  metal  more  than  the  inner  part ;  conse- 
quently it  must  have  a  tendency  to  separate  the  outer 
part  from  the  inner  part. 

It  is  more  than  probable  that  a  very  strong  cy- 
lindrical iron  forging  (suitable  for  a  gun,  or  for  one 
of  the  parts  of  a  built-up  gun)  may  be  made  by 
taking  six  Y-shape  rolled  slabs,  then  to  place  them 


48      FOKGING  AND  WELDING  IRON  AND  STEEL. 

round  a  suitable  core  of  iron,  then  to  heat  the  whole 
to  the  proper  welding  temperature,  and  then  ham- 
mering upon  the  six  sides,  and  welding  the  whole 
into  a  solid  mass.  The  mass  may  subsequently  be 
rounded  between  Y  swage-blocks ;  this  will  form  a 
good  foundation  upon  which  to  build  a  greater 
amount  of  iron. 

It  is  quite  probable  (when  rolling  these  slabs) 
that  a  projection  could  be  left  in  one,  two,  or  more 
places,  upon  one  side  of  them,  and  in  their  opposite 
sides  a  kind  of  groove  or  cutting  to  correspond  (as 
near  as  it  would  be  practicable  to  make  them)  with 
these  projections,  so  that  with  a  little  rough  fitting 
these  slabs  could  be  dovetailed  together,  and  made 
to  hold  themselves  together  whilst  being  heated  in 
the  furnace.  Plain  slabs  could  be  held  together  by 
shrinking  two  or  more  rings  upon  them,  or  they 
could  be  held  together  by  dovetailing  short  pieces 
of  bar  iron  into  them.  After  the  slabs  are  welded 
into  a  solid  mass  and  rounded  between  the  swage- 
blocks,  a  series  of  thick  rings  (made  of  rolled  bar 
iron)  must  then  be  placed  and  welded  upon  the 
mass.  These  rings  must  not  be  welded  up  pre- 
vious to  welding  them  upon  the  mass,  neither  must 
they  be  formed  by  coiling  a  long  bar  upon  the 
mass ;  the  two  ends  of  each  ring  will  require 
to  be  scarfed  in  order  that  they  may  slightly 
overlap  each  other  when  placed  upon  the  mass, 
and  not  to  form,  what  is  called  a  butt  joint.  The 
rings  being  ready,  the  forged  mass  must  now  be 
heated  to  a  white-flame  heat;  it  must  then  be  drawn 
out  of  the  furnace,  and  the  thick  scale  or  oxide 


FORGING   AND   WELDING  IRON  AND   STEEL.         49 

scraped  off;  after  which,  several  of  these  thick 
iron  rings  (or  as  many  as  may  be  convenient) 
must  be  placed  side  by  side  upon  it ;  the  rings 
should  be  placed  in  such  positions  that  their  scarfed 
joints  may  not  run  in  a  straight  line  with  each 
other ;  they  may  then  be  closed  upon  the  forged 
mass  between  Y  swage-blocks.  The 'whole  must 
now  be  placed  in  a  suitable  furnace,  and  uniformly 
heated  to  the  welding  temperature  ;  after  which,  it 
must  be  brought  to  the  hammer,  and  the  whole  weld- 
ed between  large  Y  swage-blocks ;  several  more  of 
the  rings  must  then  be  placed  upon  the  mass,  and 
side  by  side  with  the  first  rings,  and  then  heated  and 
welded  in  a  similar  manner  as  the  others,  and  so  on 
until  the  desired  length  is  obtained.  If  it  is  found 
more  convenient  to  place  and  weld  the  whole  of 
the  rings  at  once  upon  the  mass,  it  is  advisable 
to  do  so ;  for  the  fewer  the  heats  the  better  the 
forging. 

By  the  above  method,  very  few  heats  will  be  re- 
quired ;  and  we  will  have  the  fibre  of  iron  running 
in  the  direction  of  the  length  of  the  forging,  as  well 
as  in  the  direction  of  the  circumference.  The  di- 
rection of  the  fibre  is  the  strongest  way  of  iron ; 
and,  let  whatever  method  be  adopted,  we  can  only 
get  the  strength  of  the  iron.  To  have  the  fibre  of 
the  iron  running  in  the  direction  of  the  length  of 
a  rifled  gun  is  probably  of  the  greatest  impor- 
tance. 

Steel,  like  iron,  is  improved  by  hammering  and 
rolling ;  consequently,  when  a  large  cast-steel  block 
is  required  of  great  tenacity  for  a  particular  pur- 


50         FORGING   AND   WELDING   IKON   AND   STEEL. 

pose,  the  metal  is  not  run  into  a  mould  of  the  shape 
and  size  of  the  required  finished  dimensions,  but  it 
is  cast  into  a  short  thick  ingot  and  then  hammered 
and  drawn  to  the  required  finished  dimensions,  or  it 
is  rolled  to  the  required  finished  dimensions  between 
the  rollers.  Although  the  steel  is  improved  by 
being  elongated  and  solidified,  still  it  is  question- 
able whether  this  is  the  best  way  of  producing  the 
soundest  steel  block  suitable  for  a  large  gun.  If 
every  particle  of  the  metal  could  be  made  to  be- 
come cool  at  the  same  moment,  there  would  then 
be  no  question  about  this  being  the  best  method ; 
but  it  must  be  borne  in  mind  that  a  large  mass  of 
fluid  steel  cools  very  unequally :  it  cools  in  layers, 
and  closes  up  like  a  series  of  hoops,  and  is  subject 
to  very  great  strains.  It  is  obvious,  then,  that  after 
the  block  is  drawn  out  to  the  required  finished  di- 
mensions, it  still  consists  of  the  same  number  of 
layers ;  the  layers  of  course  are  reduced  in  thickness, 
which  is  unfavorable  to  the  strength  of  the  block. 
These  layers  frequently  have  so  feeble  a  cohesion 
as  to  allow  of  their  separation  by  a  very  light 
blow. 

For  the  reasons  here  given,  we  may  conclude 
that,  the  thicker  and  the  less  in  number  these  layers, 
the  stronger  the  block  must  be. 

It  is  quite  probable,  then,  that  the  soundest  for- 
ging may  be  produced  by  casting  the  block  square 
at  the  breech  end,  and  in  order  to  save  steel,  to  cast 
the  other  part  of  the  block  with  six  sides  ;  the  block 
may  be  cast  longer  and  smaller  in  diameter  than  the 
required  finished  dimensions ;  then  to  upset  it,  so  as 


FORGING   AND   WELDING   IKON   AND   STEEL.         51 

to  make  it  shorter  and  larger  in  diameter  than  the 
required  finished  dimensions  ;  it  may  then  be  elon- 
gated and  solidified  by  drawing  it  out  again  by  the 
hammer  to  the  required  finished  dimensions.  The 
breech  end  should  be  hammered  and  left  square, 
and  the  other  parts  of  the  block  (after  hammering 
upon  its  six  sides)  rounded  between  half  circles  or 
Y  svfage-tools  (the  Y  swage-tools  most  preferred). 

Casting  a  steel  block  of  the  proposed  shape,  and 
giving  it  the  proposed  subsequent  treatment,  would 
cause  more  waste  of  steel,  and  raise  the  cost  of  the 
block ;  but  it  is  quite  probable  that  the  superior 
soundness  of  it  would  more  than  compensate  for  the 
waste  of  metal,  especially  when  the  block  is  intended 
for  the  largest-size  gun.  If  it  is  intended  to  toughen 
this  block  of  steel  in  oil,  it  may  then  be  asked, 
perhaps,  whether  it  is  necessary  to  leave  the  breech 
end  square  until  after  it  has  passed  through  the 
process  of  toughening,  or  whether  it  w'ill  be  better 
to  turn  it  round.  The  answer  is,  if  the  block  is 
bored  out  to  form  a  tube  with  a  solid  end,  previous 
to  toughening  of  it,  it  will  then  be  better  to  turn 
it  round;  but  it  is  more  than  probable,  if  the 
part  which  is  left  solid  is  left  square  also,  that 
it  will  favor  the  contraction  in  cooling ;  but  it  is 
not  absolutely  necessary  to  leave  even  this  part 
square,  but  the  extreme  end  may  be  turned  and  left 
concave  in  a  slight  degree. 

If  it  was  intended  to  heat  and  immerse  the  block 
in  oil  previous  to  boring  of  it,  it  would  be  better  to 
leave  it  square  (in  the  state  it  left  the  forge)  until  it 
had  passed  through  the  process ;  but  to  attempt  to 


52         FOKGINQ-   AND   WELDING   IRON   AND    STEEL. 

toughen  it  in  its  solid  state  would  be  a  step  in  the 
wrong  direction,  as  it  would  be  sure  to  break.  ,.' 

A  common  smith's  forge  is  the  hearth  or  fire- 
place upon  which  ignited  fuel  is  placed,  and  it  very 
frequently  consists  of  masonry  or  brick-work.  It 
is  furnished  with  a  water-tank  and  coal-trough,  also 
with  a  pair  of  bellows  for  supplying  the  air.  The 
bellows  are  worked  by  a  hand  lever ;  the  small  end 
of  the  pipe  of  the  bellows  passes  through  the  back 
of  the  forge,  where  it  is  fixed  in  a  strong  iron  plate, 
called  a  tue  iron  or  patent  back,  in  order  to  preserve 
the  bellows  from  inj  ury  and  the  back  of  the  forge 
from  requiring  frequent  repair.  The  best  position 
for  the  bellows  is  on  a  level  with  the  fire-place,  al- 
though they  are  often  placed  higher,  and  the  blast 
of  air  passes  through  a  bent  tube,  in  order  to  gain 
room. 

Above  the  fire-place  is  a  hood,  which  is  some- 
times formea  of  bricks,  but  it  is  more  generally  made 
of  plate  iron ;  this  serves  to  collect  the  dust  and  the 
smoke  from  the  fire,  and  leads  it  to  the  chimney, 
and  thus  prevents  it  from  flying  about  the  shop. 
The  more  modern  forge  is  made  entirely  of  iron; 
and  the  blast  of  air  is  supplied  by  a  revolving  fan, 
worked  by  an  engine.  The  blast  is  communicated 
by  a  main  pipe  all  round  the  smithy,  and  every  fire 
has  a  branch  pipe  with  a  valve  and  handle  fitted  to 
it  for  regulating  the  blast.  The  tue  iron  at  the  back 
of  this  kind  of  forge  is  sometimes  made  hollow,  so 
that  a  stream  of  water  may  circulate  through  it  from 
a  small  tank  placed  behind  the  forge.  The  water 
keeps  the  tue  iron  from  burning,  or  getting  very  hot, 


FORGING  AND   WELDING  IRON   AND   STEEL.         53 

consequently  it  will  last  much  longer  than  the  solid 
tue  iron ;  but,  if  the  tank  is  not  kept  well  supplied 
with  water,  this  kind  of  tue  iron  will  burn  away 
much  sooner  than  the  others.  Clean  water  should 
always  be  put  into  the  tank,  and  the  tank  should  be 
supplied  with  a  cover  to  keep  out  dust  and  dirt. 

A  light  crane  is  sometimes  erected  near  the  forge 
for  managing  the  heaviest  kinds  of  work  done  by 
hand  forging.  The  forge  is  also  furnished  with  a 
poker,  shovel,  and  rake.  In  the  smithy  there  are 
anvils,  hammers,  swage-blocks,  flatters,  tongs,  chisels, 
gouges,  top  and  bottom  fullers,  top  and  bottom 
swage-tools,  drifts,  mandrels,  flat,  square,  and  round 
punches,  and  a  multiplicity  of  other  tools  of  various 
shapes  and  sizes ;  and  it  is  an  object  of  much  im- 
portance to  have  the  hammers  and  other  tools  per- 
fectly well  secured  to  the  handles,  to  prevent  serious 
accidents. 

Forges  are  sometimes  constructed  so  as  to  be 
portable,  when  the  bellows  are  most  conveniently 
placed  under  the  hearth,  and  worked  by  a  treadle 
or  hand  lever.  Sometimes  the  blast  is  supplied  by 
a  small  revolving  fan,  'attached  to  the  forge ;  the 
fan  is  driven  by  a  fly-wheel,  turned  by  hand.  Port- 
able forges  are  generally  made  of  iron,  and  those 
with  the  revolving  fan  are  generally  erected  upon 
wheels,  and  are  generally  used  by  the  amateur  me- 
chanic, by  boiler-makers  for  heating  the  rivets,  and 
repairing  their  tools.  Also  on  ships,  and  for  various 
jobs  on  bridges,  railways,  etc. 

For  forging  iron  and  steel,  for  hardening  and 
annealing  steel,  the  fire  at  the  common  forge  is  some- 


54        FOKGING-   AND   WELDING  IRON  AND   STEEL. 

times  made  open,  and  sometimes  hollow.  The  fires 
are  commonly  of  three  kinds.  The  flat  open  fire, 
the  stock  hollow  fire,  and  the  stock  open  fire ;  the 
size  of  which  must  be  regulated  by  the  requirements 
of  the  work. 

The  flat  open  fire,  when  allowed  to  burn  itself 
bright  or  clear,  is  ready  for  the  insertion  of  the 
work.  This  kind  is  generally  used  for  forging  and 
welding  small  kinds  of  work,  such  as  the  welding 
of  small  iron  rods  together,  and  the  forging  of  small 
bolts  and  nuts,  rivrets,  and  small  tools ;  in  short,  it 
is  used  for  almost  all  single-handed^work,  and  foi 
some  which  is  called  double-handed  work  (that  is, 
where  the  smith  has  an  assistant). 

The  stock  hollow  fire  for  forging  iron  is  made 
by  inserting  the  tapered  end  of  a  bar  of  round  iron 
into  the  tue  iron,  after  which  a  quantity  of  small 
wet  coal  is  thrown  upon  the  hearth  and  beat- 
en hard  round  the  bar  with  the  sledge-hammer; 
more  coal  is  then  added,  and  the  hammering  again 
repeated  ;  and  so  on,  till  the  coal  above  the  bar  is 
several  inches  in  thickness,  and  about  one  foot  more 
or  less  in  width  and  length.  After  the  hammering 
is  completed,  it  is  beaten  close  together  with  the 
slice  or  shovel  to  form  a  kind  of  embankment.  This 
is  called  the  stock.  The  bar  is  then  withdrawn,  the 
slice  or  shovel  at  the  same  time  being  held  against 
the  front  of  the  stock  to  prevent  the  bar  from  break- 
ing the  front  down.  A  second  stock  is  then  made 
opposite  the  first,  but  without  the  hole  through  the 
centre  of  it,  as  in  the  first  stock.  A  fire  is  then 
made  between  the  two  stocks,  and  the  work  laid  in 


FOKGING   AND   WELDING   IRON   AND   STEEL.         55 

the  fire ;  the  work  is  then  covered  over  with  some 
thin  pieces  of  wood  and  some  small  pieces  of  coke, 
after  which  small  damp  coal  is  .thrown  on  in  a  layer 
of  several  inches  thick,  and  beaten  down  with  the 
slice  to  form  the  roof.  A  steady  blast  is  kept  up 
all  the  time,  and  as  the  wood  burns  away  the  flame 
peepl  through  and  forms  the  mouth  of  the  fire ;  but 
the  work  is  not  moved  till  all  the  wood  is  burnt  out, 
and  the  coal  well  caked  together  into  a  hard  mass. 
More  blast  is  then  driven  in,  and  the  roof  of  the  fire 
reflects  an  immense  heat  upon  the  work  below  it. 
After  which  the  work  can  be  moved  about  in  the 
fire  or  withdrawn  without  risk  of  breaking  down  the 
fire.  A  lump  of  hard  coke  is  generally  placed 
against  the  mouth  of  the  fire  to  confine  the  heat ; 
and  as  the  fuel  in  the  inside  burns  away  it  is  re- 
placed by  pushing  in  some  small  coal,  or  soft  coke.' 
Sometimes  a  small  quantity  of  hard  coke  broken 
into  small  pieces  is  pushed  in  to  give  body  or  sub- 
stance to  the  fire.  This  kind  of  fire  is  sufficiently 
powerful  for  a  moderate  share  of  those  works  which 
require  the  use  of  a  light  crane  and  the  steam-ham- 
mer, and  which  cannot  conveniently  be  heated  in  a 
furnace ;  it  is  used  for  welding  shafts  together,  also 
for  welding  collars  upon  shafts,  and  various  other 
kinds  of  work  requiring  the  assistance  of  one,  two, 
or  more  men  ;  it  is  also  used  for  giving  a  uniform 
temperature  to  large  lumps  of  steel,  but  in  heating 
this  material  it  must  be  borne  in  mind  that  the  blast 
must  "be  sparingly  used. 

The  stock  open  fire  is  made  the  same  way  a? 
the  stock  hollow  fire,  with   the  exception  of  the 


56         FORGING   AND   WELDING   IRON  AND   STEEL. 

covering  in  or  roof.  This  is  the  raost  convenient 
fire  for  heating  the  steel  when  forging  tools ;  it  is 
also  the  most  convenient  for  heating  those  kinds 
of  tools  requiring  only  to  be  partially  heated  and 
partially  hardened,  the  remaining  part  requiring  to 
be  kept  soft,  such  as  cutting-tools  for  the  turning- 
lathe,  cold  chisels,  drills,  etc.;  but  for  those  kinds  of 
tools  which  require  to  be  heated  all  over  or  through- 
out their  body,  such  as  screw-taps,  dies,  circular 
cutters,  etc.,  the  hollow  fire  is  the  most  convenient. 

The  hollow  fire  for  heating  the  steel  for  harden- 
ing is  built  in  a  similar  manner  as  the  hollow  fire 
for  heating  steel  for  forging,  with  the  exception  that 
a  larger  quantity  of  wood  is  required  for  centring 
the  arch. 

In  forging  at  the  common  forge,  the  fire  of  course 
must  be  regulated  by  the  size  of  the  work  ;  and,  in 
heating  the  work,  if  the  flame  break  out,  the  coals 
must  be  beat  together  with  the  slice  to  prevent  the 
heat  from  escaping.  The  fire  should  be  free  from 
sulphur,  brass,  copper,  lead,  tin,  paint,  or  any  other 
thing  which  would  keep  the  iron  from  welding.  To 
save  fuel  damp  the  coal,  and  throw  water  on  the  fire 
if  it  extends  beyond  its  proper  limits.  To  ascertain 
the  state  of  the  work  it  must  be  drawn  partly  out  of 
the  fire — that  is,  when  the  open  fire  is  used — and 
thrust  quickly  in  again  if  not  hot  enough.  To  make 
the  iron  come  sooner  to  a  welding  heat,  stir  the  fire 
with  the  poker  and  throw  out  the  clinkers,  as  they 
will  prevent  the  coals  from  burning.  Care  should  be 
taken,  either  with  iron  or  steel,  not  to  use  a  higher 
degree  of  heat  than  is  absolutely  necessary  to  effect 


FORGING   AND    WELDING   IRON   AND    STEEL.         57 

the  desired  purpose,  with  steel  especially  to  use  as  few 
heats  as  possible.  The  too  frequent  and  excessive 
heating  of  steel  abstracts  the  'carbon,  and  gradually 
reduces  it  to  the  state  of  forged  iron  again.  This, 
perhaps,  calls  for  a  little  explanation.  When  steel 
is  at  a  low  heat  the  carbon  has  a  very  slight  affinity 
for  oxygen ;  hence  the  steel  suffers  little  change — 
the  change  which  does  take  place  is  so  slow  that  it 
is  not  perceptible  till  after  many  repeated  heatings ; 
but  when  steel  is  heated  to  a  high  degree  in  the 
open  fire  in  the  presence  of  oxygen,  the  surface  be- 
comes so  oxidated  that  a  scale  of  considerable  thick- 
ness peels  off,  and  with  this  scale  part  of  the  car- 
bon is  extracted  from  the  surface  of  the  steel,  and,  if 
the  temperature  of  the  steel  is  still  further  increased, 
its  affinity  for  oxygen  is  also  increased,  and  when 
approaching  the  point  of  fusion  the  affinity  becomes 
very  strong,  and  the  combustion  is,  consequently, 
rapid  ;  and  at  a  melting  heat,  in  the  presence  of  a 
large  quantity  of  oxygen,  the  carbon  cannot  exist  in 
the  steel — at  least,  only  for  a  very  short  time.  If 
further  proof  than  this  be  required,  the  reader  has 
only  to  consult  the  process  of  Mr.  Bessemer  in  man- 
ufacturing steel  or  malleable  iron  direct  from  the 
cast  iron.  Steel  which  has  been  slightly  overheated 
may  be  restored  in  a  slight  degree  by  giving  it  a 
judicious  hammering  at  a  lowered  heat.  This  will, 
however,  improve  burnt  steel  but  little,  though  the 
hammering  will  make  the  steel  denser ;  yet  no  de- 
gree of  heat  or  hammering  will  restore  to  steel  the 
carbon  or  the  original  fineness  of  texture  of  which 
it  has  been  deprived  by  being  overheated. 
3* 


58         FOKGING  AND   WELDING  IRON   AND   STEEL. 

The  heat  steel  receives  in  forging  must  also,  like 
the  heat  of  iron,  be  judged  by  the  eye;  and  the 
temperature  suitable  differs  in  some  degree  with  its 
quality  and  mode  of  manufacture :  the  heat  required 
diminishes  with  the  increase  of  carbon.  Thus  steel 
requires  much  more  precaution  as  to  the  degree  of 
heat  than  iron,  and  does  not  bear  the  same  degree  of 
heat  as  iron  without  injury ;  but  it  will  bear  a  much 
greater  amount  of  hardship  under  the  hammer  than 
iron  if  it  is  cautiously  heated. 

Steel  requires  to  be  heated  more  slowly  than  iron? 
and  requires  more  moving  about  in  the  fire  in  order 
to  equalize  the  heat  and  to  receive  a  uniform  temper- 
ature throughout ;  it  requires  also  to  be  drawn  from 
the  fire  more  frequently,  as  it  requires  to  be  well 
watched  to  heat  it  properly. 

The  tenacity  of  steel  hammered  at  a  low  heat 
is  considerably  increased ;  and,  in  forging  cutting- 
tools,  the  hammering  should  be  applied  in  the  most 
equal  manner  throughout,  and  should  be  continued 
until  nearly  cold.  But  the  effect  of  the  hammering 
is  taken  off  again,  if  the  steel  is  heated  to  a  high 
degree.  When  forging  cold  chisels,  they  ought  al- 
ways to  be  finished  with  the  flatter ;  and  they  will 
stand  better  if  the  last  blows  are  given  upon  their 
flat  sides. 

The  elasticity  of  iron  and  of  steel  hammered  cold 
is  considerably  increased — that  is,  providing  the 
hammering  is  not  carried  to  an  extreme.  Bell- 
springs  are  sometimes  made  of  sheet  steel,  and  very 
frequently  of  hoop  iron  thus  managed :  straight- 
edges, and  the  blades  of  squares  as  they  are  sold  at 


FOKGING   AM)   WELDING   IRON   AND   STEEL.         59 

the  ironmongers'  shops,  are  sometimes  made  of  tem- 
pered steel.  But  they  are  more  frequently  made 
of  sheet  steel  hammered  cold,  and  they  are  not  un- 
frequently  made  of  hoop  iron  thus  managed. 

To  change  the  form  of  iron  when  it  is  not  neces- 
sary to  weld  it,  the  white-flame  heat  is  used ;  and, 
according  to  the  size  of  the  work,  it  is  battered  by 
one,  two,  or  more  men  with  sledge-hammers.  The 
hammers  are  generally  slung  entirely  round,  with 
both  hands,  and  held  nearly  at  the  end  of  the  handle ; 
they  are  generally  directed  to  fall  upon  the  work  at 
the  centre  of  the  anvil,  and  the  work  is  gradually 
moved  backward  and  forward  to  expose  the  re- 
quired parts  to  the  action  of  the  hammers.  Two 
gangs  of  men  are  sometimes  required  for  the  larger 
work  done  at  the  common  forge ;  they  relieve  each 
other  at  intervals,  as  the  work  is  very  laborious. 
When  the  iron  is  nearly  reduced  to  the  required 
shape  and  size,  the  strength  of  the  blows  is  reduced, 
and  the  hammers  are  made  to  fall  upon  the  work 
as  nearly  flat  as  possible,  in  order  to  smooth  the 
work  after  which,  the  flatter  or  the  swage-tool  is 
held  upon  the  work,  and  the  blows  of  the  ham- 
mers are  directed  upon  the  head  of  the  tools  to  finish 
of£  the  work,  the  dexterous  use  of  which  saves 
filing, 
much  trouble  in  the  after-processes  of  chipping  and  j 

"When  it  is  required  to  thicken  any  part  of  a  bar 
of  iron  without  welding,  the  operation  called  upset- 
ting must  be  resorted  to.  This  consists  in  giving  it 
the  white-flame  heat  at  the  part  to  be  thickened, 
and,  while  one  end  rests  upon  the  anvil,  hammering 


60         FORGING  AND  WELDING   IRON   AND   STEEL. 

at  the  other  till  the  required  size  is  produced 
When  the  bar  is  large,  if  it  be  lifted  and  jumped 
upon  the  anvil,  or  upon  a  lump  of  iron  placed  upon 
the  floor,  its  own  weight  will  supply  the  required 
force  for  upsetting  it. 

When  it  is  required  to  weld  two  bars  of  iron  to- 
gether, the  sparkling  or  welding  heat  is  used.  The 
ends  are  first  upset  or  made  thicker  by  jumping 
them  endways  upon  the  anvil ;  each  end  is  then 
bevelled  off  to  a  thin  edge  (called  scarfing) ;  the  two 
ends  are  then  placed  in  the  fire,  and  raised  to  a 
welding  heat,  or  nearly  to  a  state  of  fusion  :  care  is 
required  that  both  arrive  at  the  proper  heat  at  the 
same  time.  The  bars  may  in  part  be  prevented  from 
wasting  by  taking  care  to  supply  them  at  the  heated 
part  with  powdered  glass  or  sand  just  before  they 
arrive  at  the  welding  heat ;  the  sand  or  other  material 
melts  on  the  surface  of  the  iron,  and  serves  to  form  a 
flux  or  fluid  glass  which  protects  the  iron  from  the 
impurities  of  the  fuel  and  defends  it  from  the  air,  at 
the  same  time  uniting  with  and  removing  the  oxide 
which  may  have  been  formed  on  the  heated  scarfs, 
the  removal  of  which  greatly  facilitates  the  opera- 
tion of  welding. 

When  the  two  bars  of  iron  to  be  united  have  at- 
tained the  welding  heat,  they  are  taken  out  of  the 
fire  with  the  utmost  dispatch ;  a  good  portion  of 
the  scale  or  dirt  which  would  hinder  their  uniting  is 
got  rid  of  by  striking  the  bars  across  the  anvil :  they 
are  then  placed  in  contact  at  the  heated  part,  and 
hammered  until  no  visible  seam  or  fissure  remains. 
If  they  have  not  been  sufficiently  united,  the  heat- 


FOKGING   AND  WELDING  EBON  AND   STEEL.         61 

ing  and  hammering  ought  to  be  repeated  until  the 
work  is  perfectly  sound. 

The  larger  Bars,  such  as  heavy  shafts  for  machine- 
ry, are  generally  part  welded  within  the  fire ;  the 
two  ends  are  prepared  so  that  one  fits  within  the 
other  (called  the  split  joint) ;  a  Y  piece  is  cut  out 
of  the  end  of  one  bar  with  the  chisel,  and  the  end 
of  the  other  bar  is  cut  so  as  to  fit  into  it ;  when  the 
ends  are  properly  fitted,  they  are  placed  in  their 
proper  positions  in  the  fire,  and  when  they  arrive  at 
the  proper  heat  they  are  welded  together  by  striking 
the  end  of  one  of  the  bars  with  the  sledge-hammers? 
or  by  striking  with  some  other  contrivance,  such  as 
by  a  mass  of  iron  suspended  by  a  chain  from  the 
ceiling,  while  several  men  hold  against  the  opposite 
bar  to  sustain  the  blows.  This  contrivance  is  far 
more  effective  than  the  blows  of  the  sledge-hammer, 
more  especially  when  a  thick  lump  of  iron  is  placed 
against  the  opposite  end  :  the  heat  is  kept  up  all  the 
time,  and  the  whole  is  afterward  lifted  from  the 
fire,  and  finished  upon  the  anvil.  The  amount  of 
labor  saved  by  this  kind  of  joint  for  large  works,  in 
comparison  with  the  scarf  joint,  is  considerable ;  and 
it  is  probably  the  most  effectual  way  of  getting  a 
sound  joint. 

When  a  thick  lump  is  required  on  the  end  of  a 
bar,  it  is  frequently  made  by  cutting  the  iron  partly 
through  in  several  places,  and  doubling  it  backward 
and  forward  according  to  the  thickness  required ; 
the  whole  is  then  welded  into  a  solid  mass.  Ham- 
mers are  frequently  made  from  the  iron  thus  man- 
aged, as  the  iron  is  less  liable  to  split  than  the 


62         FORGING   AND   WELDING   IRON   AND   STEEL. 

plain  bar  of  iron  in  punching  the  eye.  .  Sometimes 
the  iron  is  prepared  for  making  a  hammer,  by  weld- 
ing a  collar  (made  of  a  flat  bar)  round  a  bar  of  round 
iron  ;  at  other  times  a  flat  bar  is  heated  at  the  end 
and  rolled  up  similar  to  a  roll  of  ribbon,  and  after- 
ward welded  into  a  solid  lump.  % 

"When  a  very  thick  lump  is  required  on  the  centre 
of  a  long  bar  of  iron,  the  method  of  drawing  the  two 
ends  down  from  a  large  bar  would  be  too  expensive ; 
the  method  of  upsetting  the  bar  would  be  impracti- 
cable, consequently  a  large  collar  is  welded  round 
the  middle.  But  as  there  is  great  difficulty  in  get- 
ting a  very  wide  collar  soundly  welded  upon  the 
bar,  two  collars  half  the  width  of  the  single  collar 
are  placed  close  together  and  welded  upon  the  bar  ; 
the  two  collars  give  the  bar  a  better  opportunity  of 
attaining  the  welding  heat,  and  the  union  is  made 
perfect. 

Sometimes  a  large  collar  is  made  upon  a  bar 
of  iron  by  three  or  four  pieces  of  a  flat  bar,  heat- 
ed and  welded  on  separately ;  and  this  is  proba- 
bly the  most  effectual  way  of  getting  a  very  large 
collar  upon  the  bar.  It  is  obvious  that  the  method 
of  drawing  the  two  ends  down  from  a  large  bar  will 
produce  the  soundest  work  (providing  the  bar  itself 
be  sound) ;  but  then,  as  I  have  just  remarked,  with 
very  long  bars  it  would  be  very  expensive.  When 
a  very  large  steel  collar  is  required  to  be  welded  on 
to  a  bar  of  iron,  it  becomes  absolutely  necessary  to 
weld  it  on  in  pieces ;  because,  from  the  greater  fusi- 
bility of  the  steel,  it  is  quite  impracticable  to  weld 
a  very  wide  Bteel  collar  (made  in  one  piece)  upon  a 


FORGING  AND   WELDING  IKON   AND   STEEL.         63 

bar  of  iron,  for  the  steel  will  burn  before  the  iron 
enclosed  in  it  can  attain  the  welding  heat. 

It  is  well  known  to  practical  men  that  a  collar 
made  from  very  fusible  impure  iron  can  never  be 
effectually  welded  upon  a  bar  of  pure  fibrous  iron, 
because  an  impure  iron,  from  its  greater  fusibility, 
will  not  stand  the  heat  which  is  suitable  to  weld 
pure  fibrous  iron ;  consequently,  when  a  piece  of  a 
pure  fibrous  iron  is  enclosed  in  a  collar  made  of  an1 
impure  fusible  iron,  the  impure  iron  must  burn 
before  the  pure  fibrous  iron  can  attain  the  heat  suit- 
able to  weld  its  own  material ;  besides,  a  pure  fibrous 
iron  requires  a  flux  to  be  applied  to  it  just  before  it 
arrives, at  the  welding  heat,  while  an  impure  iron 
forms  a  flux  or  slag  from  its  own  material ;  and,  as 
an  impure  iron  burns  at  a  heat  which  is  not  sufficient 
to  weld  pure  fibrous  iron,  it  forms  a  slag  between  the 
two  irons  and  hinders  their  incorporation.  Again, 
if  the  two  different  irons  were  heated  at  different 
temperatures  suitable  to  both,  they  could  not  even 
then  be  effectually  welded  together  because  the  force 
of  the  blows  requisite  to  weld  pure  fibrous  iron  will 
disperse  fusible  impure  iron.  It  is  evident,  then, 
that  if  there  is  great  difficulty  in  welding  a  collar 
made  of  an  impure  iron  upon  a  bar  of  pure  fibrous 
iron,  that  there  will  be  still  greater  difficulty  in 
welding  a  large  steel  collar  (made  in  a  single  piece) 
upon  a  bar  of  iron  ;  therefore,  when  a  very  large 
steel  collar  is  required  upon  a  bar  of  iron,  it  becomes 
absolutely  necessary  to  weld  it  on  in  separate  pieces. 

To  weld  steel  to  steel,  then,  or  steel  to  iron,  with- 
out injuring  the  steel,  is  an  operation  which  demands 


64         FORGING   AND   WELDING-   IRON    AND   STEEL. 

great  nicety  of  management,  as  there  are  a  variety 
of  degrees  of  heat  to  deal  with.  The  welding  heat 
of  steel  is  lower  than  that  of  iron,  from  its  greater 
fusibility ;  and  the  more  fusible  the  steel  the  less 
easily  it  welds.  Highly  carbonized  cast  steel  (tool 
steel)  welds  with  greater  difficulty  than  mild  cast 
steel,  which  contains  a  smaller  proportion  of  carbon ; 
although  mild  cast  steel  is  superior  in  its  welding 
properties  to  highly  carbonized  cast  steel,  still  it 
is  inferior  in  its  hardening  properties.  The  steel 
which  contains  the  smallest  proportion  of  carbon, 
and  which  has  the  most  fibrous  texture, — as,  for 
example,  the  double  shear  steel, — is  the  most  easily 
welded ;  for,  it  having  been  most  wrought  Jby  the 
hammer,  or  between  the  rollers,  its  fibrous  character 
is  partly  restored. 

Cast  steel  is  the  most  difficult  to  weld,  on  account 
of  its  having  been  in  a  state  of  fusion,  which  entire- 
ly destroys  its  fibrous  texture. 

The  material  (sand)  which  is  used  to  serve  as  a 
flux  to  protect  and  fit  good  iron  for  welding  does 
not  answer  well  for  steel,  because  it  is  too  refracto- 
ry ;  and  some  kinds  of  cast  steel  burn  or  melt  at  a 
lower  heat  than  sand,  consequently  the  sand  would 
be  useless  to  serve  as  a  flux. 

The  material  used  to  serve  as  a  flux  for  welding 
blister  and  shear  steel  is  generally  powdered  borax, 
though  sand  is  frequently  used.  But  ordinary  cast 
steel,  from  its  greater  fusibility,  requires  a  still  more 
fusible  flux,  and,  for  this  purpose,  sal  ammoniac  is 
mixed  with  the  borax. 

The  borax  of  commerce,  as  sold  by  chemists,*^ 


FORGING   AND    WELDING   IRON    AND   STEEL.         65 


a  very  large  proportion  of  water  ;  con- 
sequently it  requires  to  be  put  into  an  iron  or  other 
suitable  vessel  and  boiled  over  the  fire  till  all  the 
water  is  expelled,  after  which  it  requires  to  be 
ground  to  powder  before  it  is  used.  When  it  is  re- 
quired to  mix  sal  ammoniac  with  borax,  the  propor- 
tions are  about  sixteen  parts  of  the  borax  to  one  of 
sal  ammoniac. 

The  material  used  to  serve  as  a  flux  for  steel  must 
be  suitable  to  protect  it,  at  the  same  time  purify  the 
surface  ;  and  should  always  be  applied  just  before 
the  metal  reaches  the  welding  heat,  no  matter  how 
high  or  low  that  heat  may  be. 

When  it  is  required  to  weld  two  bars  of  blister 
or  shear  steel  together,  they  are  heated  at  the  ends 
and  upset  or  made  thicker,  and  afterward  scarfed 
the  same  way  as  iron  bars  for  welding  ;  the  two 
ends  are  then  heated  to  a  moderate  white  heat  and 
sprinkled  with  borax;  the  temperature  is  then 
raised  to  the  proper  welding  heat  suitable  to  the 
steel.  Care  is  required  that  both  arrive  at  the 
proper  heat  at  the  same  moment,  after  which  they 
are  taken  from  the  fire  to  the  anvil  and  hammered 
till  no  visible  seam  remains. 

When  it  is  required  to  weld  two  large  bars  of 
cast  steel  together,  which  are  not  too  highly  carbon- 
ized, they  are  first  heated  at  the  ends  and  upset,  and 
scarfed  the  same  way  as  other  bars  for  welding,  with 
the  exception  that  a  thin  cutter-hole  is  punched  in 
the  scarfed  ends  of  the  cast-steel  bars  for  riveting 
them  together  previous  to  welding. 

Cast  steel  will  not  admit  of  being  made  so  soft 


66         FORGING   AND   WELDING   IEON   AND   STEEL. 

in  the  fire  as  iron  or  the  other  kinds  of  steel ;  con- 
sequently, when  it  is  first  struck  with  the  hammers, 
the  scarfs  are  more  liable  to  slip  off  each  other ;  and 
it  is  to  guard  against  this  inconvenience  that  the 
bars  are  riveted  together,  and  not  with  the  view  of 
gaining  strength  in  the  joint,  as  might  be  imagined. 
When  the  bars  are  riveted  together,  the  joint  is 
placed  in  a  bright,  clean,  and  close  fire,  the  steel  is 
heated  as  high  as  it  will  bear  without  much  injury, 
or  as  hot  as  can  be  done  with  safety  ;  the  material 
to  serve  as  a  welding  powder  or  flux  (calcined  borax 
and  sal  ammoniac)  is  then  put  on  the  heated  scarfs, 
after  which  the  steel  is  carefully  turned  over  in  the 
fire  and  supplied  with  more  of  the  powder.  It  is 
not  necessary  to  draw  the  steel  out  of  the  fire  to 
put  the  powder  on,  as  the  powder  may  be  spread  on 
the  heated  scarfs  by  a  slip  of  sheet  iron,  the  end  of 
which  requires  to  be  made  like  a  spoon ;  but,  whilst 
in  the  act  of  spreading  the  powder  upon  the  steel, 
the  blast  must  be  sparingly  used,  or  it  would  blow 
the  powder  from  off  the  spoori,  and  it  would  be 
wasted  in  the  fire. 

The  sal  ammoniac  cleans  the  dirt  from  the  steel, 
and  the  borax  causes  it  to  fuse  before  it  attains  that 
heat  which  will  burn  the  steel ;  and  when  at  the 
point  of  fusion  it  is  lifted  from  the  fire  to  the  anvil 
and  hammered  and  welded  much  in  the  same  man- 
ner as  other  kinds  of  steel  or  iron.  The  blows  are 
given  gently  at  first,  owing  to  the  weak  state  the 
steel  is  in  by  the  lessening  of  its  cohesion  by  the 
heat.  But  as  the  cohesion  of  the  steel  increases, 
the  strength  of  the  blows  is  increased  also  ;  if  the 


FOKGING   AND  WELDING   IKON"   AKD   STEEL.         67 

bars  are  not  sufficiently  united,  the  heating  and 
hammering  must  be  repeated  until  the  joint  is  per- 
fectly sound. 

When  it  is  required  to  weld  steel  to  iron,  the 
steel  must  be  heated  in  a  less  degree  than  the  iron, 
consequently  they  ought  to  be  heated  separately ; 
and,  when  they  arrive  at  the  welding  temperature 
suitable  to  both,  they  must  be  brought  to  the  anvil, 
the  dirt  which  would  hinder  their  incorporation 
must  be  brushed  off,  they  must  then  be  placed  in 
contact  with  each  other  at  the  heated  parts  and 
united  by  hammering.  Should  there  happen  to  be 
any  defective  part  in  the  weld,  the  heating  and 
hammering  must  be  repeated,  taking  care  in  the 
second  heating  (as  far  as  is  practicable)  to  keep  the 
iron  facing  -the  hottest  part  of  the  fire,  or  the  steel 
is  liable  to  be  injured. 

When  a  large  quantity  of  steel  is  required  to  be 
cut  down  into  suitable  lengths  for  screw-taps,,  or 
similar  articles,  it  is  generally  the  smith  who  is  ap- 
pointed to  cut  it  to  the  required  lengths ;  and, 
whilst  in  the  smithy,  perhaps  a  few  words  upon  the 
cutting  of  cold  steel  with  the  cold  chisel,  will  not 
be  out  of  place.  I  was*  once  working  for  an  em- 
ployer, who  had  a  large  order  for  screw-taps,  and  I 
was  appointed  to  cut  the  steel  into  lengths  with  the 
rod  cold  chisel  (a  short  thick  chisel  with  a  hazel- 
stick  twisted  round  it  to  form  the  handle);  but, 
previous  to  commencing  to  cut  the  steel,  my  em- 
ployer informed  me  that  he  did  not  much  approve 
of  cutting  the  steel  down  into  lengths  with  the  cold 
chisel,  as  he  had  discovered  a  fracture  in  a  large 


68         FORGING   AND   WELDING-   IKON   AND   STEEL. 

number  of  his  taps  which  he  had  previously  hard- 
ened, and,  as  this  fracture  was  at  the  end  of  the 
taps,  he  was  inclined  to  think  that  it  was  caused  in 
the  cutting  and  breaking  down  of  the  steel.  Being 
myself  rather  inquisitive  in  such  matters,  I  closely 
examined  the  taps,  and  found  that  the  fracture  was 
not  caused  by  the  cutting  and  breaking  down  of  the 
steel,  but  by  boring  the  centres  too  large  and  too 
deep.  Though  the  fracture  in  this  instance  was  not 
caused  at  the  time  of  the  breaking  down  of  the 
steel,  still,  it  very  frequently  happens,  that  an  in- 
ternal fracture  is  caused  in  the  steel  in  cutting 
and  breaking  it  into  lengths,  especially  when  the 
steel  is  nicked  with  a  dull  or  blunt  chisel ;  and  the 
fracture  will  not  at  all  times  be  visible  until  after 
the  steel  is  hardened ;  but  after  it  is  hardened  it 
can  readily  be  detected.  As  a  remedy  to  prevent 
this  fracture,  I  would  advise  those  who  cut  their 
steel  down  into  lengths  with  the  cold  chisel,  always 
to  keep  a  good  sharp  edge  upon  the  chisel  and  nick 
the  steel  all  round,  instead  of  only  upon  the  two 
opposite  sides  as  is  often  done.  The  steel  will  then 
break  easier  and  be  less  liable  to  splinter  on  the 
outside,  and  less  liable  to  fracture  inside. 

When  the  steel  is  too  large  to  be  conveniently 
cot  and  broken  cold,  it  will  sometimes  be  more 
economical  to  heat  the  steel  to  a  red  heat  before 
cutting  it ;  sometimes  it  will  be  more  economical  to 
cut  it  into  lengths  in  the  turning-lathe  by  means  of 
an  instrument  called  a  parting-tool. 

Steel  is  sometimes  heated  and  sawn  into  lengths 
by  means  of  a  circular  saw  driven  by  machinery, 


FOKGING    AND   WELDING   IKON   AND    STEEL.          69 

but  this  is  far  from  being  the  best  method  for  cut- 
tins:  the  best  kinds  of  cast  steel. 

O  • 

Most  workmen  when  cutting  steel  down  into 
lengths  with  the  cold  chisel,  adopt  one  or  other  of 
the  following  methods :  they  first  nick  the  steel 
with  the  chisel,  and  then  lay  the  cut  across  the 
square  hole  of  the  anvil,  in  order  that  the  steel  may 
lie  hollow,  and  then  strike  it  with  the  pane  of  the 
sledge-hammer  ;  sometimes  the  chisel  is  held  in  the 
nick,  while  the  nick  lies  across  the  hole  of  the  an- 
vil, and  the  blows  of  the  hammer  directed  upon  the 
chisel ;  the  steel  is  sometimes  made  to  lie  hollow  by 
laying  it  across  the  anvil,  at  the  same  time  holding 
a  rod  of  iron  (generally  the  poker)  beneath  it  near 
to  the  nick,  and  then  break  it  by  striking  with  the 
sledge-hammer,  the  blows  of  the  hammer  being  di- 
rected upon  the  nick ;  sometimes  the  steel  is  broken 
by  first  nicking  it  with  the  chisel  as  before,  and 
then  striking  the  bar  across  the  beak-iron  of  the 
anvil. 

It  may,  perhaps,  be  thought  by  some,  that  there 
was  no  necessity  for  speaking  upon  these  simple 
methods  of  cutting  and  breaking  steel  into  lengths ; 
but  I  have  thought  it  necessary  to  notice  them,  on 
account  of  having  witnessed  very  serious  accidents 
happen  by  adopting  these  methods,  by  the  steel 
flying  and  striking  workmen  who  happened  to  be 
working  near  where  steel  was  being  cut  and  broken. 
In  my  opinion  any  contrivance,  or  any  hint  which 
may  have  a  tendency  to  prevent  accidents,  cannot 
be  useless. 

When  it  is  necessary  to  cut  a  large  quantity  of 


70         FOKGING   AND   WELDING   IKON   AND   STEEL. 

steel  into  lengths  with  the  cold  chisel,  and  where  a 
number  of  workmen  are  at  work,  a  piece  of  tem- 
porary boarding  ought  always  to  be  placed  in  front 
of  the  anvil,  at  about  two  or  three  yards  distant 
from  the  anvil ;  the  chisel  should  be  sharp,  and  also 
properly  well  secured  to  the  handle,  as  accidents 
have  happened  from  the  neglect  of  this..  The 
striker  ought  not  to  stand  in  front  of  the  steel,  as  it 
is  very  dangerous  to  do  so ;  but  he  should  stand 
rather  on  one  side,  for,  if  the  steel  is  very  hard,  it 
will  sometimes  unexpectedly  break  with  the  first  or 
second  cut  of  the  chisel.  The  steel  ought  not  to  be 
laid  across  the  hole  of  the  anvil  to  break  it,  as  this 
is  a  very  dangerous  practice  (although  frequently 
adopted).  A  better  plan  is,  after  the  steel  has  been 
nicked  on  all  sides  with  the  chisel,  to  place  the 
swage-block  upon  its  edge,  and  then  put  the  steel 
through  one  of  the  holes,  the  piece  of  steel  to  be 
broken  being  allowed  to  project  through  the  hole. 
It  may  then  be  broken  off  with  a  very  light  blow 
of  the  hammer,  and  the  piece  of  steel  will  drop 
down  close  to  the  swage-block.  If  these  methods 
be  strictly  adhered  to,  many  a  serious  accident  will 
be  prevented. 


CHAPTER  Y. 
ANNEALING  OF  CAST  IRON  AND  STEEL. 

THERE  are  many  substances  which,  when  rapidly 
cooled  after  having  been  heated,  become  hard  and 
brittle.  Glass,  cast  iron,  and  steel  possess  this  pe- 
culiarity. Although  hardness  (as  will  subsequently 
be  shown)  is  such  a  useful  and  important  property 
in  steel,  still,  when  steel  becomes  hard  in  the  pro- 
cess of  manufacture,  or  in  the  process  of  forging  it 
into  various  kinds  of  articles,  the  hardness  becomes 
then  an  inconvenience,  at  least  when  the  articles 
require  to  be  turned,  engraved  upon,  filed,  or 
screwed ;  and  the  only  remedy  for  removing  this 
inconvenience  is  to  reheat  the  steel,  and  allow  it  to 
cool  very  gradually.  This  process  is  called  anneal- 
ing. Glass  vessels  are  generally  annealed  by  per- 
mitting them  to  cool  very  gradually  in  longer  or 
shorter  time,  according  to  their  thickness  and  bulk, 
in  an  oven  constructed  for  the  purpose.  Steel  is 
annealed  in  a  variety  of  .ways.  Some  artists  anneal 
steel  by  heating  it  to  redness  in  the  open  or  hollow 
fire,  and  then  burying  it  in  lime ;  others  heat  it 
and  bury  it  in  sand ;  others  heat  it  and  bury  it  in 
cast-iron  borings ;  others  heat  it  and  bury  it  in  dry 
sawdust,  and  some  anneal  it  by  surrounding  it  on 
all  sides  in  an  iron  box,  with  carbon,  and  then  heat 


72  ANNEALING   OF   CAST   IEON   AND   STEEL. 

the  whole  to  redness.  This  latter  process  is  un- 
doubtedly the  most  effectual  method  of  annealing 
steel ;  that  is,  providing  the  steel  is  not  heated  to 
excess.  When  this  method  of  annealing  steel  is 
adopted,  a  layer  of  wood  charcoal,  coarsely  pow- 
dered, is  placed  at  the  bottom  of  an  iron  box,  and 
then  a  layer  of  the  steel,  upon  this  another  layer  of 
charcoal,  and  upon  that  again  another  layer  of 
steel,  and  so  on  until  the  box  is  nearly  full,  finish- 
ing with  a  layer  of  charcoal.  The  lid  of  the  box 
must  then  be  put  on,  and  the  box  luted  with  clay 
or  loam,  in  order  to  exclude  the  air.  The  whole 
may  then  be  placed  in  a  furnace  or  hollow  fire,  and 
gradually  heated  to  redness.  The  size  and  shape 
of  the  box,  it  is  obvious,  must  vary  with  the  shape 
and  quantity  of  the  steel  requiring  to  be  operated 
upon.  It  must  be  borne  in  mind  that  the  same  care 
is  required  in  heating  the  steel  in  this  process  as 
there  is  in  heating  the  steel  for  forging  or  harden- 
ing. Overheating  the  steel  in  any  £>ne  of  the  pro- 
cesses is  hurtful.  It  is  seldom  necessary  to  keep  up 
the  heat  beyond  the  time  that  the  contents  of  the 
box  are  uniformly  heated,  unless  the  steel  should 
happen  to  contain  particles  of  hard  impure  iron, 
when  it  would  then  be  necessary  to  keep  up  the 
heat  for  several  hours.  When  the  whole  has  ar- 
rived at  the  proper  temperature  the  box  may  then 
be  withdrawn  from  the  fire  and  buried  in  some  hot 
or  cold  ashes  to  become  quite  cool,  or  may  be  left 
in  the  fire,  and  the  fire  allowed  to  cool  down.  It 
is  quite  necessary,  however,  that  the  steel  should  be 
protected  from  air  until  it  becomes  cool.  After  be- 


ANNEALING   OF   CAST   IRON   AND    STEEL.  73 

coming  cool,  and  being  taken  out  of  the  box,  it  is 
then  in  a  fit  state  for  the  fitting  or  turning  room. 
The  steel  will  then  be  very  soft  and  free  from  those 
hard  bright  spots  which  workmen  call  pins,  and 
which  are  impediments  to  the  filing  and  turning  of 
steel.  If  the  steel  and  the  charcoal  have  been  prop- 
erly protected  from  the  air,  the  surface  of  the  steel 
will  be  as  free  from  oxidation  as  it  was  before  it 
was  heated,  and  the  greater  portion  of  the  charcoal 
will  remain  unconsumed,  as  it  has  been  preserved 
from  combustion ;  consequently  it  has  undergone 
little  change,  with  the  exception  of  being  hardened, 
and  its  color  changed  to  a  deeper  black.  It  can 
therefore  be  pat  aside  to  be  used  again.  This  mode 
of  annealing  prevents  the  steel  from  losing  any  of 
its  quality  ;  but  the  steel  absorbs  by  the  process  a 
small  quantity  of  carbon,  which  is  favorable  to  the 
steel  in  the  hardening  process,  which  will  be  ex- 
plained in  the  chapter  upon  the  hardening  of  steel. 
It  may  be  well  to  state  that  animal  charcoal  is  some- 
times used  as  wrell  as  wood  charcoal  for  annealing. 

Less  than  a  certain  heat  will  fail  to  make  steel 
hard,  but,  on  the  contrary,  will  soften  it ;  and  some- 
times this  effect  is  useful.  For  instance,  suppose  a 
piece  of  steel  (for  any  special  purpose)  is  wanted  in 
a  hurry,  and  suppose  the  steel  has  become  by  ham- 
mering too  hard  to  be  dressed  with  the  file,  or  cut 
with  the  turning-tool,  and  time  will  not  admit  of 
its  being  softened  in  a  box  with  charcoal  powder 
the  steel  may  be  heated  to  a  cherry-red  heat  in  an 
open  fire,  then  be  drawn  out  of  the  fire,  and  allowed 
to  cool  down  till  the  red  heat  is  not  visible  by  day- 


74:  ANNEALING   OF   OAST   EBON   AND   STEEL. 

light,  but  can  be  seen  in  a  dark  place  beneath  or 
behind  the  forge,  then  to  be  plunged  at  this  heat 
into  cold  water,  and  allowed  to  remain  in  the  water 
until  it  becomes  quite  cool.  When  taken  out  of 
the  water  it  will  be  found  to  be  more  uniform  in 
temper  than  when  it  left  the  forge ;  consequently 
it  will  work  more  pleasantly  with  the  file  or  the 
turning-tool.  This  is  a  very  expeditious  way  of  an- 
nealing steel ;  but  the  steel  will  not  be  quite  so  soft 
as  steel  which  is  enclosed  in  the  iron  box,  and  an- 
nealed in  contact  with  charcoal  powder. 

There  are  many  who  do  not  know  the  value  of 
a  good  tool  because  the  steel  they  work  upon  has 
not  been  properly  annealed,  and  before  the  tool  has 
half  done  its  duty  it  is  either  worn  out  or  wants  re- 
pairing; whereas,  if  the  steel  had  been  properly 
annealed,  the  same  tool  would  have  lasted  very 
much  longer  without  needing  repair.  Steel  re- 
quired to  be  annealed  in  such  large  quantities  as  to 
make  it  inconvenient,  or  the  expense  of  enclosing  it 
in  boxes  too  great,  may  be  heated  in  a  charcoal  tire 
completely  enveloped  and  protected  from  the  air. 
After  the  steel  has  become  heated  to  the  proper 
temperature,  the  fire  and  the  steel  may  be  covered 
over  with  pieces  of  plate  iron.  The  whole  may 
then  be  covered  over  with  cinder-ashes  and  the  fire 
allowed  to  go  out  of  its  own  accord.  It  will  thus 
be  protected  until  it  is  cold.  Charcoal,  especially 
when  it  is  used  as  fuel  in  the  open  fire,  is  consumed 
with  rapidity,  and  therefore  very  expensive.  The 
steel  may,  however,  be  heated  in  a  cinder  fire, 
which  is  less  expensive  in  the  cost  of  an  equal 


ANNEALING   OF   CAST   IRON   AND   STEEL. 

measure  and  also  in  the  rate  of  its  consumption. 
This  kind  of  fuel  is  not  so  pure  as  charcoal,  but  it 
is  purer  than  coal,  and  affords  a  very  moderate 
heat.  "When  the  steel  is  at  the  proper  heat  it  must 
be  taken  out  of  the  cinder  fire  and  placed  in  an  iron 
box  containing  coarsely  powdered  charcoal;  the 
charcoal  must  completely  envelop  the  steel,  and  the 
box  will  require  to  be  covered  up  and  luted  with 
clay  or  loam,  in  order  to  exclude  the  air  and  pre- 
serve the  charcoal  for  future  use. 

Cast  iron  may  be  annealed  in  a  similar  manner 
as  steel.  Cast  iron  in  the  state  it  leaves  the  moulds 
is  always  surrounded  with  a  crust  or  coating,  some- 
thing similar  to  the  coating  of  steel  which  surrounds 
case-hardened  iron  ;  and  this  coating  is  sometimes  so 
extrem'ely  hard  that  the  best  file  or  turning-tool  will 
make  no  impression  upon  it,  while  the  interior  of 
the  casting  is  soft  and  manageable.  This  hard  crust 
is  generally  removed  by  the  workmen  either  by  chip- 
ping it  with  the  cold  chisel,  or  by  grinding  it  on  a 
large  grinding-stone,  turned  by  machinery.  But 
when  the  shape  of  the  casting  is  such  that  this  crust 
cannot  conveniently  be  removed  with  the  chisel  or 
the  grinding-stone,  annealing  then  is  the  most  eco- 
nomical process,  as  it  makes  the  whole  casting  soft 
and  much  easier  to  wrork,  but  still  does  not  deprive 
it  of  its  natural  character. 

To  anneal  cast  iron  the  heat  requires  to  be  kept 
up  much  longer  than  for  steel.  Cast  iron  requires  to 
have  solid  supports  to  keep  it  from  bending  or  break- 
ing by  the  heat.  Cast  iron,  like  steel,  when  annealed, 
is  more  uniform  in  temper ;  consequently  it  is  less 


6  ANNEALING   OF   CAST   IRON   AND   STEEL. 

liable  to  alter  its  figure  by  a  subsequent  partial  expo- 
sure to  moderate  heat,  than  that  which  has  not  been 
annealed. 

The  outside  of  cast  iron,  even  when  it  is  annealed, 
is  always  somewhat  harder  than  the  internal  part, 
unless  such  processes  be  adopted  as  will  abstract  the 
carbon  fi;om  the  exterior  part ;  but  these  processes, 
it  is  obvious,  deprive  it  of  its  natural  character  and 
make  it  in  the  condition  of  malleable  iron,  but 
without  the  fibre  which  is  due  to  the  hammering 
and  rolling.  Cast-iron  cutlery  is  enclosed  in  boxes 
and  cemented  with  some  substance  containing  oxy- 
gen, such  as  poor  iron  ores  free  from  sulphur,  the 
scales  from  the  smith's  anvil,  and  various  other  ab- 
sorbents of  carbon.  The  boxes  are  luted  in  a  simi- 
lar manner  as  the  boxes  when  annealing  steel  or 
case-hardening  iron ;  they  are  afterward  placed,  in 
suitable  furnaces  and  the  cast  articles  are  kept  in  a 
state  little  short  of  fusion  for  two  or  three  days ; 
they  are  then  found  to  possess  a  considerable  degree 
of  malleability,  and  can  be  readily  bent  and  slightly 
forged.  Copper  forms  an  exception  to  the  general 
rule  of  annealing;  copper  is  actually  made  softer 
and  more  flexible  by  plunging  it  when  red  hot  into 
cold  water,  than  by  any  other  means.  The  gradual 
cooling  of  copper  in  a  similar  manner  as  steel  or 
cast  iron  produces  a  contrary  effect.  "When  copper  is 
required  very  soft  and  the  surface  very  clean,  a 
small  quantity  of  sulphuric  acid  (vitriol)  may  be  put 
into  the  water,  which  will  have  the  effect  of  remov- 
ing all  the  black  scale  from  its  surface. 


CHAPTER  VI. 
HARDENING  AND  TEMPERING  OF  STEEL. 

WE  have  now  arrived  at  a  very  important  pro- 
cess, justly  termed  the  crowning  process.  It  is  that  of 
hardening  the  articles ;  and,  if  the  proper  steel  has 
not  been  chosen  for  the  articles,  or  if  the  proper  steel 
has  been  chosen  and  has  not  afterward  been  properly 
treated  through  all  the  stages  which  it  has  had  to  pass, 
or  if  the  hardener  be  not  fully  aware  of  the  general 
principles  upon  which  he  must  proceed,  all  past 
efforts  may  prove  futile.  It  is  not  requisite  that  the 
hardener  should  be  a  chemist ;  but  some  slight  ac- 
quaintance at  least  with  chemistry,  or  of  the'  action 
of  substances  upon  each  other,  will  be  extremely 
serviceable  to  him.  To  be  unqualified  in  this  re- 
spect will  be  laboring  in  the  dark :  a  successful  re- 
sult may  often  be  obtained ;  but  it  will  be  very  im- 
perfectly known  how  it  happened,  and  it  will  afford 
no  valuable  instruction  for  the  future. 

There  are  too  many  who  entertain  an  opinion 
that  they  have  nothing  new  to  learn  which  is  worth 
notice ;  they  are  apt,  in  effect,  to  say,  that,  having 
served  an  apprenticeship  to  their  business,  they  ought 
to  know  something,  and  because  they  ought  to  know 
something,  they  seem  to  expect  submission  to  their 
very  errors.  To  such  I  speak  not ;  to  convince  them 


78  HARDENING   AND   TEMPERING   OF    STEEL. 

| 

would  be  impossible,  and  therefore  the  attempt  folly. 
But  the  prudent  artisan,  whose  first  care  is  generally 
to  provide  himself  with  tools  adapted  to  his  labors^ 
I  would  ask  to  improve  his  knowledge  of  that  ma- 
terial, the  proper  choice  and  management  of  which 
constitutes  the  first  step  toward  success  in  mechan- 
ical pursuits. 

The  art  of  hardening  and  tempering  steel  con- 
stitutes one  of  the  most  delicate,  curious,  and  useful 
branches  connected  with  mechanical  art ;  it  is  an  art 
of  long  standing,  and  always  one  of  anxiety,  but 
by  whom  or  when  it  was  first  adopted  I  am  not  pre- 
pared to  decide.  In  this  place  it  claims  notice  on 
account  of  its  contributing  so  essentially  to  the  per- 
fection of  all  the  other  arts.  The  great  steam-en- 
p'nes,  iron  bridges,  Atlantic  cables,  and  iron  ships 
of  the  present  day,  are  much  indebted  to  this  branch 
of  art ;  and  without  it  the  six  hundred-pounder  guns, 
or  even  the  Great  Exhibition  itself,  might  never 
have  been  seen.  A  proper  inquiry,  therefore,  into 
ttrfs  delicate  branch  of  art  must  prove  very  useful 
to  the  engineer,  as  well  as  to  the  young  beginner, 
and  may  not  prove  uninteresting  even  to  the  gen- 
eral reader,  especially  when  processes  which  do  not 
generally  appear,  and  are  not  often  communicated 
by  workmen,  are  explained.  At  first  sight  the  art 
of  hardening  and  tempering  steel  appears  sufficient- 
ly simple,  when  by  heating  a  piece  of  steel  to  red- 
ness, and  plunging  it  into  cold  water,  it  becomes 
hard  ;  on  a  closer  inspection,  however,  the  mind  Mill 
soon  discover  that  many  operations  and  contrivances 
require  to  be  carried  into  effect  by  the  hardener  in 


HARDENING   AND   TEMPERING   OF    STEEL.  9 

order  to  become  efficient  in  his  art,  or  to  be  distin- 
guished for  skill  and  promptitude  in  execution.  A 
slight  knowledge  of  the  processes  will  also  discover 
that  a  certain  amount  of  patient  perseverance  is 
required — an  amount  of  which  few  who  have  been 
brought  up  at  the  desk,  or  behind  the  counter,  can 
form  the  slightest  idea.  But  I  have  not  set  out  with 
the  object  to  discourage  the  young  practitioner,  but' 
rather  to  encourage  him  and  smooth  for  him  the 
path  which  I  have  myself  found  so  rough,  but  which 
I  have  always  endeavored  to  explore  without  enter- 
taining a  sentiment  of  its  hardship ;  and  I  would 
advise  all  young  men  who  are  just  starting  in  the 
world  to  go  and  do  likewise. 

Before  proceeding  further,  I  would  state,  that  I 
have  not  undertaken  to  explain  every  thing  in  con- 
nection with  this  subject ;  but  my  main  object  in  the 
present  chapter  is  to  explain,  in  a  plain  way,  the 
chief  causes  why  steel  breaks  in  hardening ;  also  to 
notice  some  of  the  contrivances  which  I  have  found 
in  my  own  experience  to  be  the  least  expensive,  and 
most  easily  reducible  to  practice  ;  the  most  suitable 
to  prevent  steel  from  breaking ;  and,  if  the  informa- 
tion be  properly  studied,  it  will  enable  the  mechanic 
to  harden  and  temper  any  kind  of  article  with  which 
he  may  have  to  do. 

Many  theories  upon  the  cause  of  steel  becoming 
hard  by  the  process  of  heating  and  suddenly  cooling 
it  have  been  formed  ;  but  they  are  so  beset  with  diffi- 
culties and  uncertainty,  that  in  my  opinion  the  prop- 
er cause  has  not  yet  been  proved.  I  have  previous- 
ly shown  that  steel  is  a  compound  of  iron  and  carbon ; 


80  HARDENING  AND  TEMPERING   OF   STEEL. 

and,  as  pure  iron  does  not  harden  by  simple  immer- 
sion, it  must  be  to  its  carbon  that  steel  owes  this 
valuable  property;  and,  if  I  may  be  allowed  to 
theorize  on  the  reason  why  steel  becomes  hard  by 
sudden  cooling,  I  should  be  inclined  to  state  that  it 
is  the  crystallization  of  the  carbon,  caused  by  com- 
pression and  sudden  cooling,  and,  being  combined 
with  the  iron,  becomes  a  hard  and  solid  substance ; 
but,  let  this  be  so  or  not,  there  is  one  thing  certain, 
that  a  new  arrangement  of  the  particles  takes  place 
by  the  process  of  hardening.  But,  as  I  shall  have 
an  occasion  to  speak  upon  this  hereafter  (in  the  chap- 
ter upon  the  expansion  and  contraction  of  steel),  it 
will  be  superfluous  to  speak  upon  it  in  this  place, 
but  rather  confine  myself  to  the  mechanical  opera- 
tions of  the  subject. 

It  is  of  considerable  importance  that  the  designer 
of  tools  or  other  articles  should  have  some  knowledge 
of  the  quality  of  the  material  to  be  used ;  likewise 
he  should  have  some  knowledge  of  the  action  of 
fire  and  water  upon  the  material ;  also  he  should 
have  some  knowledge  of  the  practice  of  the  hard- 
ener. 

The  workmen,  through  whose  hands  the  articles 
must  pass,  either  in  the  fitting  or  the  turning  room, 
should  also  have  some  knowledge  of  the  art  of  hard- 
ening ;  in  fact,  it  is  as  requisite  that  fitters  and  turn- 
ers should  have  some  knowledge  of  the  practice  of 
the  hardener  and  the  action  of  fire  and  water  upon 
the  steel,  as  it  is  for  the  pattern-maker  to  have  some 
knowledge  of  the  practice  of  the  moulder. 

The  superior  character  of  castings  depends  in  a 


HARDENING-  AND  TEMPERING  OF  STEEL.     81 

great  measure  upon  the  superior  skill  which,  has 
been  displayed  upon  the  patterns  ;  and  the  success  in 
the  hardening  of  steel,  in  many  instances,  depends 
ito  a  great  measure  upon  the  ingenuity  displayed  in 
the  fitting  or  the  turning  room,  and  also  on  the  in- 
genuity displayed  in  designing  the  article. 

Too  little  attention  is  generally  paid  to  the 
quality  of  the  material  when  required  for  very  par- 
ticular tools,  or,  in  other  words,  for  tools  that  require 
a  great  amount  of  labor  and  time  to  make  them ; 
and  in  the  fitting  or  the  turning  room,  or  even  in 
the  drawing-office,  the  expansion  and  contraction 
of  steel  is  seldom  heeded  or  even  thought  of,  though 
it  is  of  the  greatest  importance. 

When  it  is  required  to  make  an  expensive  article, 
and  where  there  is  great  risk  of  its  breaking  in  the 
hardening,  the  first  thing  to  be  done  is  to  select  the 
proper  steel  for  the  purpose  and  afterward  to  an- 
neal it  to  the  fullest  extent ;  if  an  equal  and  judi- 
cious hammering  be  given  to  the  steel  by  the  smith 
before  it  is  annealed  it  gives  a  density  to  the  steel 
and  the  article  will  be  more  durable;  besides,  it 
will  lessen  the  risk  of  its  breaking  in  the  hardening, 
but  the  effect  of  the  hammering,  as  I  have  before 
remarked,  is  taken  off  again  by  strong  ignition,  and 
the  smith's  labor  is  lost,  therefore  it  is  evident  that 
there  is  as  much  care  required  in  heating  the  steel 
when  it  is  required  to  be  annealed  as  there  is  in 
heating  it  when  it  is  required  to  be  forged  or  hard- 
ened. When  the  steel  is  annealed  it  is  then  in  a  fit 
state  for  the  fitting  or  the  turning  room,  there  to  be 
fashioned  into  the  required  article. 
4* 


82  HARDENING   AND   TEMPERING-   OF   STEEL. 

The  artist  employed  upon  it  ought  to  bear  in 
mind  that  steel  breaks  in  hardening  from  its  unequal 
contraction  at  different  parts ;  the  danger  increases 
with  the^thickness  and  bulk,  and  the  more  especially' 
when  certain  parts  are  unequally  thick  and  thin, 
consequently  before  finishing  any  article  for  hard- 
ening one  thing  should  be  attended  to,  which  I  will 
attempt  to  explain,  and,  if  I  succeed  in  making  it 
understood,  the  artist  will  have  obtained  information 
as  to  the  plans  to  be  adopted  with  large  articles 
generally.  It  is  this :  examine  the  article  and  see 
which  part  of  it  is  likely  to  be  the  last  to  become 
cold  when  it  is  immersed  in  the  water,  and  if  it  is" 
practicable  to  reduce  the  steel  in  that  part  without 
inconveniencing  the  article  it  is  advisable  to  do  so ; 
the  steel  will  then  cool  more  uniformly  and  be  less 
liable  to  fracture.  If  it  were  possible  to  get  every 
particle  of  the  steel  cold  at  the  same  moment,  there 
would  be  an  end  to  the  danger  of  steel  breaking  in 
hardening ;  but,  as  this  cannot  be  done,  we  must 
approach  it  as  near  as  we  can. 

For  the  better  understanding  of  the  subject,  let 
us  suppose  that  a  large  circular  cutter,  such  as  are 
used  for  shaping  and  trueing  of  work  of  various 
shapes,  is  required  to  be  made,  we  will  suppose  it 
to  be  required  about  seven  inches  in  diameter  and 
two  inches  in  thickness,  with  numerous  cutting- 
edges  (termed  teeth)  round  the  circumference,  and 
a  round  hole  in  the  centre  through  which  to  pass 
the  spindle.  It  is  obvious  that  the  first  thing  which 
will  require  to  be  done  will  be  to  select  the  proper 
steel  for  the  cutter  and  afterward  to  forge  it  to  the 


HARDENING  AND  TEMPERING  OF  STEEL.     83 

required  dimensions,  after  winch  it  will  require  to 
be  annealed  to  the  fullest  extent ;  but  as  the  choos- 
ing, forging,  and  annealing  have  already  been 
treated  of,  it  will  be  superfluous  to  speak  more  upon 
it  in  this  place,  consequently,  let  us  suppose  the 
steel  in  its  forged  and  annealed  state  to  be  obtained. 
The  -first  thing  usually  done  after  the  steel  is  ob- 
tained is  to  bore  the  mandrel-hole,  after  which  it  is 
turned  to  the  required  thickness,  and  the  two  sides 
of  the  block  of  steel  left  flat ;  the  superfluous  metal 
upon  the  circumference  is  then  turned  off,  which 
leaves  the  block  of  the  required  diameter.  The 
teeth  are  now  cut  upon  the  circumference  of  this 
block  of  steel,  either  by  means  of  a  file  or  by  a  tool 
whose  edge  is  of  the  proper  form,  and  can  be  used 
either  in  a  planing  or  shaping  machine,  or  even 
with  the  lathe.  But  the  most  perfect  teeth  are  cut 
by  means  of  another  rotary  cutter,  whose  edge  is 
of  the  proper  form,  and  working  in  a  machine  con- 
structed for  the  purpose.  It  is  usual  to  bore  the 
mandrel-hole  in  large  cutters,  the  same  size  as  the 
mandrel-hole  in  the  smaller  size  cutters,  so  that 
both  large  and  middle  size  cutters  may  fit  the  same 
mandrel,  but  this  is  a  step  in  a  wrong  direction. 
The  larger  the  cutter  the  larger  the  mandrel-hole 
should  be — not  to  say  that  the  mandrel  itself  would 
not  be  strong  enough ;  but  a  large  mandrel-hole  in 
large  cutters  favors  the  cutters  in  hardening  by  al- 
lowing the  steel  to  cool  more  uniformly ;  whereas 
a  small  mandrel-hole  in  a  large  cutter,  having  two 
plain  flat  sides  or  surfaces,  increases  the  risk  of  the 
cutter  breaking  in  hardening,  Though  a  large 


84  HARDENING  AND   TEMPERING-  OF   STEEL. 

mandrel- hole  favors   a  large  cutter  in  hardening, 

O  O  7 

still  it  is  not  absolutely  necessary  to  have  a  large 
mandrel-hole  in  them,  because  large  cutters  having 
a  small  mandrel-hole  in  them  may  be  hardened 
without  breaking  them,  by  taking  care  previou  s  to 
hardening  them  to  reduce  the  substance  of  the 
steel. 

The  substance  of  the  steel  must  be  reduced  in  that 
part  of  the  cutter  which  is  the  last  to  become  cool 
when  it  is  immersed  in  the  water.  It  is  -obvious 
that  the  part  which  is  the  last  to  become  cold  will 
be  halfway  between  the  mandrel-hole  and  the  cir- 
cumference, consequently  large  cutters  will  require 
to  be  dished  out  or  turned  concave  on  both  sides ; 
or  if  a  few  smaller  holes  than  the  mandrel-hole  be 
bored  round  the  mandrel-hole,  it  will  answer  the 
same  purpose  as  turning  each  side  concave.  Either 
of  the  above  plans  will  greatly  red  uce  the  risk  of 
all  large  cutters  breaking  in  hardening,  and  it  does 
not  materially  reduce  their  strength  or  stability. 

It  is  obvious  that  the  method  of  turning  the 
sides  of  large  cutters  concave  cannot  be  adopted 
with  cutters  which  require  to  have  teeth  on  their 
sides  as  well  as  on  their  circumference ;  still  holes 
could  be  bored  through  these,  and  probably  it 
would  not  in  the  least  prevent  the  cutter  from 
doing  its  work ;  still  the  cutter  would  not  have  a 
very  pleasing  appearance,  and  it  would  not  look 
very  mechanical.  Consequently,  instead  of  boring 
holes  in  these  kinds  of  large  cutters,  it  will  be 
better  to  make  the  mandrel-hole  large  in  propor- 
tion to  the  cutter. 


HARDENING   AND   TEMPERING   OF   STEEL.  85 

Perhaps  it  will  be  of  some  use  to  hint,  as  it  is  a 
very  valuable  hint  if  properly  taken,  that  a  circular 
cutter  of  any  required  thickness,  and  seven  inches 
in  diameter,  and  which  has  a  three-inch  mandrel- 
hole  through  its  centre,  is  less  liable  to  break  in 
hardening  than  a  circular  cutter  of  the  same  thick- 
ness, sfo  inches  in  diameter,  and  which  has  a  two- 
inch  mandrel-hole  through  its  centre. 

There  are  numbers  of  articles  besides  cutters 
which  require  to  be  hardened,  where  it  becomes 
necessary  to  bore  holes  in  them,  or  cut  out  a  kind  of 
panel  to  make  them  cool  more  equally.  In  some 
instances  boring  holes  in  steel  articles  requiring  to 
be  hardened  is  injurious  or  unfavorable  to  the  arti- 
cles in  hardening.  For  instance,  boring  holes  too 
near  the  outside  edges  of  some  kinds  of  articles  will 
sometimes  cause  the  article  to  crack  at  the  hole. 

It  may  be  well  to  state  that  drilling  a  hole  or 
centre  too  large  or  too  deep  into  screw-taps  or  ri- 
mers, and  various  other  articles  which  require  to  be 
hardened,  is  a  great  evil  and  should  in  general  be 
avoided ;  for,  when  the  centres  are  too  large  or  too 
deep,  it  weakens  the  ends  of  the  articles,  and  it  not 
only  weakens  the  ends  of  the  articles,  but  it  fre.- 
quently  causes  a  fracture  in  the  ste'el  at  the  bottom 
of  the  centre. 

In  all  cases,  if  the  centres  are  not  required  in  the 
articles  after  they  are  hardened,  it  is  advisable  to  file 
them  out  previous  to  hardening  them,  and  thus  pre- 
vent all  risk  of  their  getting  cracked  at  that  part  in 
hardening. 

In  making  steel  tools  or  steel  articles  of  any  de- 


86     HARDENING  AND  TEMPERING  OF  STEEL. 

scription  sharp  internal  angles  should  in  general  be 
avoided,  as  they  are  very  unfavorable  in  the  hard- 
ening process ;  consequently  the  key- ways  in  cutters 
should  be  half  circle.  In  all  kinds  of  articles  sharp 
internal  angles  are  unfavorable  to  the  strength  of 
the  articles,  so  that  it  becomes  necessary  to  leave  all 
the  internal  corners  a  little  rounded. 

It  may  be  useful,  perhaps,  to  add  that  cutters 
which  are  required  for  cutting  soft  substances,  such 
as  brass  or  copper,  require  to  have  their  teeth  very 
sharp,  and  to  be  made  very  hard.  The  teeth  require 
also  to  be  cut  much  coarser  than  for  iron  or  steel, 
otherwise  they  soon  become  choked  with  the  metal, 
and  become  hot,  and  very  soon  lose  their  sharp  edges, 
and  will  not  cut,  as  the  term  is,  sweet,  but  would  pol- 
ish and  glide  over  the  metal  almost  without  effect, 
were  the  cutters  not  seconded  by  a  great  amount  of 
power. 

When  a  steel  tool  or  piece  of  work  similar  in 
shape  to  a  piece  of  a  bar  of  round  steel,  say,  two, 
three,  four,  or  more  inches  in  diameter,  and  three, 
four,  five,  or  more  inches  in  length  is  required  to  be 
hardened,  it  frequently  becomes  necessary,  previous 
to  hardening  such  a  tool  or  piece  of  work,  to  bore  a 
hole  through  the  centre  of  it,  in  the  direction  of  its 
length,  in  order  that  the  water  may  pass  through 
the  hole,  and  cool  the  steel  more  equally,  and  reduce 
the  risk  of  its  breaking.  But  as  the  two  ends  are 
even  then  always  likely  to  become  cool  first,  it 
would  not  be  amiss  to  widen  the  hole  a  little  more 
in  the  centre  than  at  the  ends,  and  so  further  reduce 
the  risk  of  its  breaking  in  hardening. 


HARDENING   AND   TEMPERING   OF   STEEL.  87 

*  It  is  unnecessary,  perhaps,  to  remark,  that  the 
largest  size  screw-taps  and  hobs  are  very  liable  to 
break  in  hardening,  and,  though  a  hole  might  be 
bored  through  them  to  prevent  their  breaking,  still 
this  would  not  give  a  very  pleasing  appearance,  nor 
would  it  look  very  mechanical.  Independent  of  the 
appearance  of  the  tap  or  hob,  a  hole  through  large 
screw-taps  or  hobs  would  be  very  apt  to  cause  them 
to  become  oval  in  hardening ;  and  if  this  did  occur 
it  would  cause  the  tap,  when  in  use,  to  make  the  hole 
larger  than  it  was  intended  to  do,  and  cause  the  hob 
when  in  use  to  cut  very  unequally  and  very  slowly, 
because  only  two  opposite  sides  of  the  hob  could  be 
made  to  cut. 

It  is  obvious  that  a  round  piece  of  steel  having  a 
plain  or  smooth  surface,  and  which  has  a  hole  bored 
through  it  in  the  direction  of  its  length,  would  be  as 
likely  to  become  oval  in  hardening  as  a  piece  of 
steel  having  a  similar  hole  through  it  and  a  screw 
upon  its  surface,  such  as  a  tap  or  hob.  But  then 
there  are  means  by  which  a  plain  surface  can  be 
made  true  again  after  hardening,  such  as  by  lap- 
ping or  grinding,  whereas  with  taps  or  hobs  these 
methods  cannot  be  adopted.  In  all  cases  it  must 
be  borne  in  mind  that,  the  more  uniformly  articles 
are  heated,  the  less  liable  are  they  to  become  crooked 
or  oval  in  hardening. 

For  the  various  reasons  above  given,  another 
method  differing  from  the  boring  of  holes  through 
large  taps  or  hobs  may  be  adopted,  a  method  which 
will  not  at  all  disfigure  the  taps  or  hobs,  or  cause 
them  to  become  oval,  but  which  will  cause  them  to 


88     HARDENING  AND  TEMPERING  OF  STEEL. 

harden  and  cool  more  uniformly,  at  the  same  time 
prevent  them  breaking.  It  is  this :  to  turn  the 
plain  part  of  the  tap  or  hob  as  small  as  it  will  con- 
veniently bear  without  encroaching  upon  the  re- 
quired strength  of  the  tap  or  hob,  and  to  cut  the 
concave  grooves  (which  are  in  the  direction  of  the 
length  of  the  best  kinds  of  taps)  a  little  deeper  than 
what  they  are  generally  cut. 

The  method  of  reducing  the  steel  in  that  part  of 
large  articles  which  is  the  last  to  become  cold  when 
they  are  immersed  in  the  water,  cannot  with  some 
kinds  of  articles  be  adopted ;  because,  were  the  steel 
to  be  reduced  in  that  particular  part,  it  would  unfit 
the  articles  for  the  purpose  for  which  they  are  in- 
tended. This  would  be  the  case  with  large  circular 
dies,  which  frequently  require  to  be  turned  flat  on 
both  sides.  It  is  obvious  that  the  method  of  boring 
holes  through  these  kinds  of  articles,  or  turning  the 
sides  of  them  concave,  cannot  be  adopted  ;•  con- 
sequently another  method  must  be  resorted  to.  It 
is  this  :  to  heat  an  iron  ring  or  collar,  and  while  the 
die  is  in  a  cold  state  shrink  the  heated  ring  tight 
upon  the  die ;  this  method  will,  when  the  die  is 
heated  and  immersed  in  the  water,  lessen  the  risk 
of  fracture. 

It  will  be  imagined,  perhaps,  that  the  object  of 
shrinking  a  ring  upon  the  die  is  to  compress  the 
die,  and  by  compressing  the  die  it  will  keep  it  from 
breaking  ;  now,  if  this  were  the  object,  it  would  be 
a  step  in  the  wrong  direction.  The  object  of  shrink- 
ing a  ring  upon  the  die  is  to  prevent  the  water  from 
cooling  the  outside  of  the  die  too  suddenly.  It 


HARDENING    AND   TEMPERING   OF    STEEL.  89 

must  be  borne  in  mind  that  the  more  suddenly  the 
heat  is  extracted  from  the  steel,  the  more  sudden  is 
the  contraction  of  the  surface  steel ;  and  the  more 
sudden  the  contraction  of  the  surface  steel,  the  more 
sudden  and  greater  is  the  compression  of  the  in- 
terior steel ;  and  the  more  sudden  and  greater  the 
compression  of  the  interior  steel,  the  greater  is  the 
risk  of  the  steel  breaking  by  the  outer  crust  being 
held  for  the  moment  in  a  greater  state  of  tension 
(strain).  The  more  the  interior  steel  is  compressed 
the  more  dense  it  becomes ;  consequently,  when  it 
becomes  cold  it  occupies  less  space  than  what  it  oc- 
cupied previous  to  hardening,  and  the  result  is  an 
internal  fracture. 

It  will  not  be  out  of  place,  perhaps,  to  remark, 
that  if  every  mechanic  were  made  more  acquainted 
with  the  chemical  properties  of  the  material,  and  the 
action  of  fire  and  water  upon  the  material,  thousands 
@f  articles  which  have  been  thrown  aside  might  have 
been  prevented  from  being  burnt  in  forging,  and  thou- 
sands more  would  have  been  saved  from  being  cracked 
in  hardening  ;  and  the  price  paid  upon  the  forging, 
annealing,  turning,  fitting,  and  hardening,  or  making 
articles  from  bad  material,  might  have  been  saved. 

Suppose  a  similar  block  of  steel  to  the  one  just 
treated  of  to  be  required  for  a  large  friction-wheel, 
the  method  of  shrinking  a  ring  upon'  it  previous  to 
hardening  of  it  will  not  answer,  because  the  ring 
would  prevent  the  water  from  effectually  hardening 
the  steel  in  that  part  which  is  required  the  hardest ; 
consequently  the  same  methods  will  have  to  be 
adopted  with  this  kind  of  article  as  those  which  are 


90     HARDENING  AND  TEMPERING  OF  STEEL. 

to  be  adopted  with  a  large  circular  cutter,  either 
boring  holes  through  it  or  turning  the  sides  concave. 
Suppose  an  eccentric  steel  collar  is  required  to  be 
hardened,  for  example.  Let  us  suppose  the  hole  in 
the  collar  where  the  shaft  or  mandrel  passes  through 
to  be  about  two  inches  in  diameter,  and  the  thick- 
ness of  the  metal  one  inch  and  a  half  on  one  side 
and  about  the  quarter  of  an  inch  on  the  opposite 
side,  from  the  irregular  form  of  this  article  it  will 
easily  be  seen  that  there  is  great  risk  of  its  breaking 
in  hardening.  The  unequal  thickness  of  the  steel 
causes  unequal  contraction,  one  side  of  the  collar 
being  so  thin  it  is  cool  almost  instantly.  The  stout 
side  contracts  after  the  thin  side  is  fixed,  the  thin 
side  .in  its  then  hard  state  cannot  give,  consequently, 
it  breaks.  Before  such  an  article  as  this  is  sent  to 
the  hardener,  a  piece  of  iron  should  be  fitted  to  the 
thin  side  of  it  so  as  to  make  both  sides  about  equal 
in  thickness.  The  iron  must  be  fitted  to  the  inside, 
as  it  is  the  outside  of  the  collar  which  is  required 
hard.  This  piece  of  iron  is  to  prevent  the  thin  part 
of  the  collar  from  cooling  too  suddenly,  and  thus 
prevent  the  collar  breaking.  The  piece  of  iron,  of 
course,  must  be  bound  upon  the  collar  with  a  piece 
of  binding  wire,  after  which  it  is  ready  for  harden- 
ing. I  may  here  remark,  that  a  square  lump  of 
steel  is  less  liable  to  break  in  hardening  than  either 
a  cylindrical  or  spherical  lump,  even  though  there  be 
more  bulk  in  the  square  lump  than  what  would 
form  either  the  spherical  or  the  cylindrical  lump. 

Although  this  is  such  an  important  subject,  and 
much  more  might  be  said,  still  it  is  not  necessary, 


HARDENING  AND  TEMPERING  OF  STEEL.     91 

perhaps,  to  enlarge  more  upon  it,  as  the  mind  will 
have  discovered  by  this  time,  the  method  of  proceed- 
ing with  tools  or  articles  of  any  description  requir- 
ing a  great  amount  of  labor  and  time  to  make  them  ; 
and  where  there  is  great  danger  of  their  breaking 
in  hardening.  The  same  or  similar  methods  will 
have  to  be  adopted  in  all  cases  where  large  masses 
of  steel  require  to  be  hardened,  if  we  wish  to  obtain 
satisfactory  results. 

The  information  here  afforded,  coupled  with 
the  workman's  own  experience  and  ingenuity,  will, 
doubtless,  be  sufficient  to  prevent  his  finding  diffi- 
culty in  forming  for  himself  any  particular  idea  upon 
the  subject  he  may  want ;  consequently  I  will  now 
pass  on  to  the  process  of  hardening  and  tempering. 

In  the  process  of  hardening  steel,  water  is  by 
no  means  essential,  as  the  sole  object  is  to  extract 
its  heat  rapidly ;  and  the  more  sudden  the  heat  is 
extracted,  the  harder  the  steel  will  be ;  consequent- 
ly, those  substances  which  act  most  suddenly  upon 
the  steel  will  produce  the  greatest  effect,  though 
they  will  not  always  produce  the  most  satisfactory 
results,  for  intense  cold  has  a  very  unfavorable 
effect  upon  steel.  Good  cast  steel  receives  by  sud- 
den cooling  a  degree  of  hardness  almost  equal  to 
that  of  the  diamond,  and  almost  sufficient  to  cut, 
or  make  an  impression,  upon  every  other  substance; 
and,  when  of  the  best  quality,  and  the  hardness  not 
carried  to  extreme,  a  certain  amount  of  tenacity  is 
also  combined  with  the  hardness. 

If  steel  is  heated  to  a  red  heat,  and  allowed  to 
cool  gradually,  it  becomes  nearly  as  soft  as  pure 


92     HARDENING  AND  TEMPERING  OF  STEEL. 

iron,  and  may,  nearly  with  the  same  facility,  be 
worked  into  any  required  form.  If  steel  be  too 
hard,  it  will  not  be  proper  for  tools,  or  instruments 
of  any  description,  which  are  required  to  have  very 
keen  edges,  or  very  fine  points,  because  it  will  be 
so  brittle  that  the  edges  will  soon  become  notched, 
or  the  points  break  off  on  the  slightest  application 
to  the  work ;  if,  on  the  contrary,  the  steel  be  too 
soft,  the  edges  or  points  will  turn  or  bend ;  but,  if 
the  steel  is  duly  tempered,  it  will  resist  breaking 
on  the  one  hand  and  bending  on  the  other. 

The  degree  of  heat  required  to  harden  steel  is 
different  in  the  different  kinds.  The  best  kinds 
require  only  a  low  red  heat ;  the  lowest  heat  neces- 
sary to  effect  the  desired  purpose  is  the  most  ad- 
vantageous, and  to  impart  to  it  any  extra  portion 
of  heat  must  partly  destroy  its  most  valuable  prop- 
erties ;  and  for  this  misfortune  there  is  no  remedy, 
for,  if  cast  steel  is  overheated,  it  becomes  brittle, 
and  can  .never  be  restored  to  its  original  quality ; 
therefore,  it  will  be  quite  incapable  of  sustaining  a 
cutting  edge,  but  will  chip  or  crumble  away  when 
applied  to  the  work. 

There  are  various  ways  of  applying  the  heat  to 
articles  when  they  require  to  be  hardened.  The 
methods  to  be  adopted  will  of  course  depend  upon 
the  shape  and  size  of  the  articles ;  also,  upon  the 
quantity  requiring  to  be  operated  upon,  for  in  some 
instances  a  large  quantity  can  be  heated  and  hard- 
ened as  expeditiously  as  a  .  single  article.  Some- 
times it  is  requisite  to  heat  the  articles  in  the  midst 
of  the  fuel  in  a  hollow  fire ;  sometimes  it  is  requi- 


HARDENING   AND   TEMPERING   OF    STEEL.  93 

site  to  heat  them  in  an  open  fire ;  and  sometimes 
it  is  requisite  to  enclose  and  surround  them  with 
carbon  in  a  sheet-iron  case,  or  box,  and  heat  the 
whole  in  a  hollow  fire,  or  in  a  suitable  furnace  ;  at 
other  times,  or  in  some  instances,  it  is  more  conve- 
nient to  heat  them  in  red-hot  lead.  When  a  large 
quantity  of  some  kinds  of  articles  is  required  to  be 
hardened,  the  method  of.- heating  them  in  red-hot 
lead  is  very  convenient  and  very  economical ;  but  to 
be  constantly  employed  dipping  articles  in  red-hot 
lead  is,  I  believe,  very  injurious  to  health.  I  have 
myself  been  so  employed,  and  have  felt  its  very  bad 
effects ;  and  I  have,  therefore,  Avoided  using  it  as  a 
source  of  heat,  except  in  cases  of  great  necessity. 

A  more  uniform  degree  of  heat  can  be  given  to 
some  articles  by  heating  them  in  red-hot  lead,  than 
by  any  other  means,  especially  some  kinds,  which 
.are  of  great  length ;  consequently,  they  will  keep 
their  proper  shape  better  in  hardening.  A  gas- 
flame,  or  the  flame  of  a  candle,  is  very  convenient 
for  heating  the  point  of  some  small  articles ;  some 
small  articles  may  be  sufficiently  heated  by  placing 
them  between  the  red-hot  jaws  of  a  pair  of  tongs. 
Some  small  articles  may  be  heated  by  taking  a 
piece  of  bar-iron,  and,  after  heating  it  to  redness, 
cutting  it  half  way  through  with  the  chisel,  and 
then  placing  the  articles  in  the  nick,  which  will 
heat  them  sufficient  for  hardening.  Sometimes  it  is 
necessary  to  insert  a  piece  of  iron  pipe  in  the  midst 
of  the  ignited  fuel  of  the  fire,  and  then  to  place  the 
articles  in  the  pipe. 

When  a  large    number  of   steel   articles   are 


94     HAEDENING  AND  TEMPERING  OF  STEEL. 

required  to  be  hardened  all  over,  or  throughout 
their  body,  and  which  are  too  small  to  be  heated  in 
the  midst  of  the  ignited  fuel  of  a  hollow  or  open 
fire,  and  perhaps  it  is  inconvenient  to  heat  them  in 
red-hot  lead,  or  if  it  be  thought  hazardous  to  enclose 
them  entirely  in  a  sheet-iron  box,  from  an  appre- 
hension that  the  heat  might  increase  too  much,  the 
following  scheme  may  be  adopted.  Place  as  many 
of  the  articles  at  once  as  may  be  convenient  to 
manage  into  a  sheet-iron  pan,  without  a  lid,  and 
cover  them  with  charcoal  dust,  place  the  whole  in 
a  furnace  or  hollow  fire,  and  slowly  heat  them  to 
redness.  They  should  be  occasionally  and  carefully 
moved  about  in  the  pan  by  the  use  of  a  small  wood 
or  iron  rod,  in  order  to  equalize  the  heat ;  the  char- 
coal dust  prevents  the  articles  from  scaling  so  read- 
ily, and  has  a  tendency  to  prevent  the  rod  bending 
them  when  moving  them  about  in  the  pan.  When- 
the  articles  arrive  at  the  proper  heat  they  may  be 
immersed  in  water  or  oil,  or  water  with  a  film  of 
oil  upon  the  surface,  according  to  the  degree  of 
hardness  required  in  them. 

A  rod  of  good  steel  in  its  hardest  state  is  broken 
almost  as  easily  as  a  rod  of  glass  of  the  same  dimen- 
sions, and  this  brittleness  can  only  be  diminished 
by  diminishing  its  hardness ;  and  in  this  manage- 
ment consists  the  art  of  tempering.  The  surface 
of  the  hardened  steel  is  brightened,  and  it  is  exposed 
to  heat.  As  the  heat  increases  there  is  a  curious 
and  uniform  change  in  the  clear  color  of  the  sur- 
face. The  colors  which  appear  upon  the  surface 
of  the  steel  are  supposed  to  be  the  result  of  oxida- 


HARDENING   AND   TEMPERING  OF   STEEL.  95 

tion.  The  thickness  of  the  coat  or  film  of  oxide,  if 
such  it  be,  determines  the  color,  and  the  thickness 
of  the  coat  depends  upon  the  temperature  to  which 
the  work  is  exposed. 

It  is  quite  probable  that  these  colors  are  the 
result  of  oxidation ;  but  the  present  state  of  my 
knowledge  does  not  enable  me  to  prove  that  these 
colors  would  not  appear  if  the  steel  could  be  heated 
in  a  vacuum,  a  space  unoccupied  with  air,  neither 
does  the  present  state  of  my  knowledge  enable  me 
to  prove  that  these  colors  are  not  due  to  the  new 
arrangement  of  the  particles,  quite  independent  of 
any  chemical  change ;  but,  let  the  cause  be  what 
it  may,  these  colors  are  a  very  useful  index,  for  by 
them  any  degree  of  hardness  retained  by  the  steel 
may  be  ascertained.  The  colors  which  successively 
appear  on  the  surface  of  the  steel,  slowly  heated, 
are  a  yellowish  white  or  light  straw  color,  a  dark 
straw,  gold  color,  brown,  purple,  violet,  and  deep 
blue.  Finally,  the  steel  becomes  red  hot,  and  a 
black  oxide  is  formed.  It  will  be  more  readily 
imagined  that  the  various  colors  are  the  result  of 
oxidation,  when  it  is  seen  that  the  action  of  the 
oxygen  of  the  atmosphere  upon  the  steel  in  a  red- 
hot  state  converts  the  surface  of  the  steel  into  a 
black  oxide ;  and  this  black  oxide,  like  the  various 
colors,  increases  in  thickness  with  increase  of  tem- 
perature, and  if  it  is  hammered  or  scraped  off  it  is 
again  quickly  formed. 

There  are  various  ways  of  applying  the  heat  for 
tempering  or  reducing  the  hardness  in  steel  articles. 
The  methods  to  be  adopted  -will,  of  course,  depend 


96  HARDENING   AND   TEMPERING   OF   STEEL. 

upon  the  shape  and  size  of  the  articles ;  also  upon 
the  quantity  requiring  to  be  operated  upon  ;  for  in 
some  instances  a  large  quantity  can  be  tempered  as 
expeditiously  as  a  single  article.  The  heat  for  tem- 
pering should  not  be  too  suddenly  applied,  as  a  cer- 
tain amount  of  time  is  essential  for  the  particles  to 
rearrange  themselves,  and  the  slower  the  heat  is 
applied  the  tougher  and  stronger  the  steel  becomes. 
When  it  is  required  to  temper  an  article  or  articles 
to  any  of  the  colors  previously  spoken  of,  they  must 
be  brightened  after  they  are  hardened.  But  before 
proceeding  farther  it  will  perhaps  be  well  to  state 
that  previous  to  brightening  the  articles  the  hard- 
ener ought  always  to  make  himself  sure  that  the 
!  articles  are  quite  hard.  If  the  articles  are  not  prop- 
erly hardened,  or,  in  other  words,  if  the  articles  are 
not  possessed  of  a  certain  degree  of  hardness,  it  will 
be  time  and  labor  lost  afterward  to  temper  them ; 
besides,  the  articles  will  be  practically  useless  for 
the  purpose  they  are  intended  for  until  they  have 
been  hardened  -and  tempered  over  again.  There- 
fore, in  order  to  make  sure  of  good  work,  the  hard- 
ener should  always  try  the  hardness  of  the  steel 
with  a  smooth  file,  a  file  finely  cut.  It  has  already 
been  inquired  of  me,  and  may  be  inquired  again, 
perhaps,  why  is  it  necessary  for  a  practical  man 
who  is  thoroughly  acquainted  with  the  quality  of 
the  material  he  is  hardening,  likewise  with  the 
temperature  suitable  to  harden  the  material,  to  try 
the  hardness  of  the  steel,  when  he  knows  from  ex- 
perience that  tlxe  steel  hardens  properly  at  a  certain 
temperature  ?  The  answer  to  this  is,  the  hardener 


HARDENING   AND   TEMPERING   OF   STEEL.  97 

may  be  a  practical  man,  and  may  be  thoroughly 
acquainted  with  the  quality  of  the  material,  like- 
wise with  the  temperature  suitable  to  harden  the 
material ;  but  if  he  is  not  a  careful  man  his  knowl- 
edge will  be  of  little  service,  and  the  necessity  for 
trying  the  hardness  of  the  steel  before  it  is  tempered 
is  soon  made  evident :  besides,  if  proper  attention 
is  not  paid  to  the  water  it  will  deceive  the  hardener. 
Again,  the  most  careful  and  experienced  hardener 
is  liable  to  be  deceived  in  the  temperature  of  the 
steel  when  hardening  in  twilight.  It  has  previously 
been  stated,  that  it  is  requisite  at  times  to  enclose 
some  kinds  of  articles,  when  they  require  to  be 
hardened,  in  a  sheet-iron  box,  and  surround  them 
with  charcoal.  When  this  method  is  adopted,  the 
articles  will  require  a  much  more  considerable 
amount  of  time  to  heat  them  than  is  readily  ima- 
gined by  those  who  are  not  accustomed  to  this 
method.  Charcoal  is  a  bad  conductor  of  heat,  and 
if  the  hardener  be  unacquainted  with  the  conduct- 
ing quality  of  the  charcoal,  he  will  be  apt  to  draw 
the  box  out  of  the  fire  and  immerse  the  contents  in 
the  water,  before  the  central  articles  have  acquired 
the  proper  temperature  suitable  for  hardening  them, 
and  those  articles  which  are  below  a  certain  heat 
cannot  become  hard.  Here  again  is  exhibited  the 
necessity  of  trying  whether  all  the  articles  are  hard 
before  beginning  to  temper  them.  In  some  instan- 
ces (though  the  steel  be  the  very  best  that  Sheffield 
can  furnish),  one  or  two  badly  tempered  articles 
would  get  the  manufacturer  of  them  a  bad  name, 

and  would  in  some  instances  get  all  the  order  con- 
5 


98  HARDENING  AND  TEMPERING   OF   STEEL. 

\ 

demned,  even  if  all  the  other  articles  were  right. 
The  use  of  the  file  for  proving  whether  the  articles 
are  hard  can  be  dispensed  with  when  the  articles 
are  brightened  on  an  emery-wheel,  or  a  small  dry 
grinding-stone  running  at  a  quick  speed,  for  the 
person  employed  to  brighten  them  will  find,  if  they 
are  properly  hardened,  plenty  of  brisk,  lively  sparks 
fly  from  them  when  they  are  held  upon  the  emery- 
wheel  or  the  grinding-stone.  But  if  they  are  not 
Ihard  there  will  be  very  little  fire  in  them.  There- 
fore, with  a  very  little  attention,  these  articles  which 
are  soft  (if  any  there  be)  can  be  detected,  and  may 
be  put  aside  and  heated  again  with  the  next  batch. 

After  the  articles  are  brightened,  the  hardness 
t  can  be  reduced  to  any  particular  standard,  by  pla- 
cing them  upon  a  hot  bar  or  plate  of  iron,  or  upon 
the  surface  of  melted  lead,  or  in  a  bath  of  a  more 
fusible  metal  kept  at  a  certain  heat,  or  in  hot  sand, 
or  burning  charcoal,  or  the  articles  may  be  held  in 
the  inside  of  an  iron  ring  heated  to  redness,  or  they 
may  be  placed  in  the  mouth  of  a  furnace,  or  in  an 
oven  heated  to  the  proper  temperature,  or  they  may 
be  placed  in  or  upon  a  gas-stove  specially  con- 
structed, or  they  may  be  heated  in  any  other  con- 
venient way. 

The  above  methods  of  applying  the  heat  for 
tempering  are  to  suit  those  kinds  of  articles  which 
have  been  wholly  quenched.  When  any  of  the 
above  methods  of  applying  the  heat  is  adopted,  and 
the  articles  are  exposed  to  a  higher  degree  of  heat 
than  that  which  is  required  to  reduce  them  to  the 
exact  temper,  they  must  be  removed  from  the  heat 


HARDENING  AND  TEMPERING  OF  STEEL.     99 

immediately  they  attain  the  desired  color,  other- 
wise the  temper  will  become  too  far  reduced,  or  in 
other  words  the  articles  will  be  too  soft  for  the  pur- 
pose they  are  intended  for.  After  they  are  removed 
from  the  heat  they  may  be  immersed  in  water  or 
oil,  or  they  may  be  allowed  to  cool  in  the  air  of 
their  own  accord;  for  it  matters  not  which  way 
they  become  cold,  providing  the  heat  has  not  been 
too  suddenly  applied  ;  for  when  the  articles  are  re- 
moved from  the  heat  they  cannot  become  more 
heated,  consequently  the  temper  cannot  become 
more  reduced.  But  those  kinds  of  tools  which  are 
heated  further  than  what  they  are  required  hard, 
such  as  a  large  portion  of  the  small  kinds  of  turning- 
tools,  cold  chisels,  and  the  larger  kinds  of  drills,  and 
numbers  of  other  kinds  of  tools,  and  which  are  only 
partially  dipped,  and  which  are  afterward  tem- 
pered by  the  heat  from  the  back  of  the  tool,  must 
be  cooled  in  the  water  the  moment  the  cutting  part 
attains  the  desired  color,  otherwise  the  body  of  the 
tool  will  continue  to  supply  heat,  and  the  cutting 
part  will  become  too  soft. 

It  is,  perhaps,  too  obvious  to  require  remark, 
unless  it  be  for  the  information  of  those  who  are  un- 
accustomed to  these  processes,  that  if,  after  temper- 
ing an  article  it  proves  too  hard  for  the  purpose  it 
is  intended  for,  it  is  not  absolutely  necessary  to 
reharden  it,  though  in  some  instances  it  is  more  con- 
venient to  do  so,  the  temper  may  be  further  reduced 
by  exposing  it  again  to  heat ;  but,  if  an  article  is 
too  far  reduced  in  temper,  it  becomes  then  absolute- 
ly necessary  to  harden  it  over  again.  When  a  very 


100         HARDENING   AND   TEMPERING   OF   STEEL. 

large  number  of  small  articles  are  required  to  be 
tempered,  it  will  be  too  slow  a  process  to  temper 
them  to  a  certain  color;  therefore,  a  more  expedi- 
tious method  must  be  adopted.  A  very  convenient 
way  of  tempering  a  large  quantity  of  small  article's 
at  once,  and  of  heating  them  uniformly,  no  matter 
how  irregular  their  shape,  providing  the  heat  is  not 
too  suddenly  applied,  is  to  put  them  into  a  suitable 
iron  or  copper  vessel  with  as  much  tallow  or  cold 
oil  as  will  just  cover  them,  and  then  to  place  the 
whole  over  a  small  fire  and  slowly  heat  the  oil  un- 
til a  sufficient  heat  is  given  to  the  articles  for  the 
temper  required.  It  may  be  well,  perhaps,  to  re- 
mind the  young  mechanic  that  the  temperature  of 
the  oil  or  tallow  may  be  raised  to  six  hundred  de- 
grees of  heat,  or  rather  more ;  consequently,  any 
temperature  below  a  red  heat  may  be  given  to  the 
articles  by  the  heated  oil.  Certain  degrees  of  tem- 
per retained  by  steel  articles  when  they  are  heated 
in  oil  may  be  estimated  by  the  following  circum- 
stances :  when  the  oil  or  tallow  is  first  observed  to 
smoke,  it  indicates  the  same  temper  as  that  called 
a  straw  color.  The  temperature  of  the  oil,  if  meas- 
ured tar  the  thermometer,  will  be  about  450  de- 
grees. ^^ 

If  the  heat  be  continued,  the  smoke  becomes 
more  abundant,  and  of  a  darker  color;  this  indi- 
cates a  temper  equal  to  a  brown.  The  tempera- 
ture of  the  oil  at  this  stage,  if  measured  by  the  ther- 
mometer, will  be  about  500  degrees.  If  the  oil  or 
tallow  be  heated  so  as  to  yield  a  black  smoke  and 
still  more  abundant,  this  will  denote  a  purple  tern- 


HARDENING  AND  TEMPERING  OF  STEEL.    101 

per.  The  temperature  of  the  oil  at  this  stage,  if 
measured  by  the  thermometer,  will  be  about  530  de- 
grees. The  next  degree  of  heat  may  be  known  by 
the  oil  or  tallow  taking  fire  if  a  piece  of  lighted 
paper  be  presented  to  it,  but  yet  not  so  hot  as  to 
burn  when  the  lighted  paper  is  withdrawn.  This 
will  denote  a  blue  temper.  The  temperature  of  the 
oil  at  this  stage,  if  measured  by  the  thermometer, 
will  be  about  580  degrees.  If  the  articles  are  lifted 
out  of  the  vessel  at  this  period,  they  will  be  found 
to  possess  a  considerable  amount  of  elasticity.  This 
temper  is  not  unfit  for  some  kinds  of  springs,  but 
only  when  a  rather  mild  kind  of  steel  is  employed  ; 
the  steel  in  this  state  may  be  wrought,  that  is,  it 
may  be  turned  or  filed,  though  with  difficulty. 

The  next  degree  of  heat  may  be  known  by  the  oil 
or  tallow  taking  fire  and  continuing  to  burn,  at  the 
same  time  rising  higher  in  the  vessel.  If  the  arti- 
cles are  lifted  out  of  the  vessel  at  this  period,  the 
oil  will  burn  upon  them  with  a  white  flamed  This 
is  the  temper  which  is  mostly  used  for  spiral  and 
some  other  kinds  of  springs. 

If  the  whole  of  the  oil  or  tallow  be  allowed  to 
burn  away  before  the  articles  are  lifted  out  of  the 
vessel,  it  imparts  the  temper  which  clock-makers 
mostly  use  for  their  work.  This  temper  is  the  low- 
est used,  when  the  steel  is  required  to  be  at  all  harder 
than  in  its  natural  state  ;  for  a  small  degree  of  heat 
more  would  just  be  seen  (red)  in  a  dark  place. 

Any  single  article,  to  spare  the  trouble  of  heat- 
ing it  in  a  vessel  with  oil  or  tallow,  may  be  smeared 
with  oil  or  tallow  and  held  over  a  clear  fire,  or  over 


102 


HARDENING  AND  TEMPERING  OF  STEEL. 


a  piece  of  hot  iron  ;  or,  if  the  article  is  small,  it  may 
be  held  in  a  gas -flame,  or  in  the  flame  of  a  candle, 
and  its  temper,  when  heated,  ascertained  in  a  similar 
manner.  It  will  not,  perhaps,  be  out  of  place  to 
state,  that  I  was  once  asked  by  a  young  man  the 
way  to  harden  and  temper  spiral  springs  made  of 
steel  wire.  I  informed  him  that  he  must  first  of  all 
harden  them  either  in  water  or  oil,  according  to  the 
substance  of  the  steel ;  and,  if  he  had  a  sufficient 
quantity  to  do  which  would  pay  for  the  waste  of  the 
oil,  it  would  be  a  very  convenient  and  expeditious 
method  to  tie  them  all  together  with-  a  piece  of 
iron  wire,  and  place  them  in  an  iron  saucepan  or 
•  any  other  suitable  vessel  he  might  chance  to  have, 
with  as  much  oil  or  tallow  as  would  cover  them, 
and  then  to  place  the  whole  over  a  small  fire, 
and  slowly  continue  the  heat  until  the  oil  takes  fire, 
and  continues  to  burn ;  after  which,  to  lift  the 
springs  out  of  the  vessel  by  means  of  an  iron  rod, 
and  then  to  give  them  one  dip  into  some  cold  oil. 
This  was  to  give  the  springs  a  black  color ;  they 
were  then  to  be  allowed  to  cool  in  the  air  of  their 
own  accord. 

When  I  gave  the  above  information,  I  did  not 
think  for  one  moment  that  this  young  man  would 
attempt  to  boil  the  oil  over  the  fire  in  the  dwelling- 
house  ;  but  he  informed  me  that  he  did  so,  and  the 
result  was  that  he  nearly  set  the  house  on  fire.  I 
have  just  mentioned  this  circumstance  merely  as  a 
warning  to  those  who  are  unacquainted  with  the 
nature  of  oil  at  this  high  temperature,  so  that  they 
may  not  fall  into  the  same  error;  they  must  not 


HARDENING  AND  TEMPERING  OF  STEEL.    103 

attempt  to  boil  oil  unless  they  have  a  place  suitable 
for  it,  or  serious  accidents  may  happen. 

Before  putting  any  article  in  the  fire  to  heat  it 
for  hardening,  it  is  necessary  to  examine  its  shape 
in  order  to  know  which  way  it  will  require  to  be 
immersed  in  the  water  so  as  to  lessen  the  risk  of  its 
cracking ;  every  kind  of  article  requires  to  be  dipped 
a  particular  way  according  to  its  shape.  For  in- 
stance, if  the  article  is  unequally  thick  and  thin,  or  in 
other  words,  if  there  is  a  stout  part  and  a  thin  part, 
the  stoutest  part  should  always  enter  the  water  fore- 
most. By  dipping  the  article  with  the  stoutest  part 
of  it  entering  the  water  foremost,  it  causes  the  steel 
to  cool  more  uniformly,  and  lessens  the  risk  of  frac- 
ture. If  the  thinnest  part  of  the  article  be  allowed 
to  enter  the  water  foremost,  it  increases  the  risk  of 
fracture,  because  it  will  become  cool  much  sooner 
than  the  stouter  part  of  the  article,  consequently 
the  stout  part  of  the  article  contracts  by  the  loss  of 
heat  after  the  thin  part  is  fixed ;  the  thin  part  in  its 
then  hard  and  brittle  state  cannot  give,  consequent- 
ly it  breaks ;  or,  if  it  does  not  break  at  the  time  of 
the  hardening  of  it,  it  is  held  in  such  a  state  of 
tension  (strain)  that  it  is  ready  to  break  when  ap- 
plied to  the  work. 

Though  it  is  requisite  when  hardening  steel 
articles  to  let  the  stoutest  part  of  the  articles  enter 
the  water  foremost,  in  order  to  allow  the  steel  to 
become  cool  more  uniformly,  still  it  is  not  practi- 
cable in  all  instances  to  get  the  stoutest  part  of  the 
articles  into  the  water  foremost,  as  will  subsequent- 
ly be  shown. 


104:        HAKDEOTNQ   AND  TEMPEKINO   OF   STEEL. 

When  it  is  not  practicable  to  get  the  stoutest 
part  of  some  kinds  of  articles  into  the  water  fore- 
most, some  other  method  which  will  keep  the  thin 
part  of  the  articles  from  cooling  too  suddenly,  and 
which  will  cause  the  steel  to  become  more  uniform- 
ly cool,  must  be  resorted  to.  The  various  methods 
to  be  adopted  for  lessening  the  risk  of  fracture 
when  hardening  various  kinds  of  articles,  will  be 
explained  as  we  go  along. 

The  water  which  is  to  be  used  for  hardening 
steel  tools,  or  any  other  kind  of  articles  made  of 
steel,  should  never  be  quite  cold,  but  should  have, 
as  the  term  is,  the  chill  taken  off;  or,  to  use  other 
words,  the  water  requires  to  be  made  a  few  degrees 
warmer.  The  reason  for  this  is,  that  when  water, 
of  too  cold  a  temperature  is  used,  it  abstracts  the 
heat  so  suddenly  from  the  surface  of  the  steel,  that 
it  causes  a  too  sudden  contraction  of  the  surface 
steel,  and  the  expansion  of  the  interior  steel  in  its 
still  red-hot  state  is  more  than  the  hardened  crust 
can  bear,  consequently  it  frequently  causes  the  steel 
to  break.  • 

It  is  quite  probable  that  the  interior  steel  for 
the  moment  becomes  both  heated  and  expanded  in 
a  higher  degree  by  the  sudden  compression,  for  the 
sudden  contraction  of  the  surface  steel  by  the  sud- 
den loss  of  heat  must  act  on  the  interior  steel  some- 
thing similar  to  a  blow  from  a  heavy  hammer  or 
the  pressure  of  a  squeezer ;  and  if  the  steel  should 
happen  to  be  a  little  too  hot  at  the  time  of  dipping 
it  into  pure  cold  water,  there  is  as  much  danger  of 
its  breaking  as  there  is  of  a  glass  bottle  breaking 


HARDENING   AND   TEMPERING   OF    STEEL.         105 

when  boiling  water  is  poured  into  it ;  heat  and 
cold  act  on  glass  and  other  brittle  substances  in  a 
similar  manner  that  they  act  on  steel.  When  boil- 
ing water  is  poured  into  a  glass  bottle,  the  expan- 
sion of  the  inside  glass  is  so  sudden  that  it  is  more 
than  the  outside  can  bear,  consequently  the  bottle 
breaks ;  if  the  glass  is  heated  to  a  red  heat  and 
plunged  into  cold  water,  it  breaks  into  a  quantity 
of  small  pieces  from  the  sudden  contraction ;  if  a 
stone  is  thrown  into  the  fire,  it  breaks  from  the  sud- 
den expansion  of  its  surface. 

The  more  the  water  is  used  for  hardening  steel 
the  softer  it  becomes,  and  has  a  tendency  to  act  less 
suddenly  upon  the  steel ;  consequently  the  less  fre- 
quently the  water  used  for  the  purpose  is  changed 
the  better  it  is  for  hardening  the  steel — that  is,  pro- 
viding the  water  has  not  by  continual  use  become 
greasy.  The  water  is  not  made  better  for  giving 
the  steel  a  greater  degree  of  hardness  by  being  long 
in  use,  but  it  is  made  better  for  the  purpose  because 
it  is  less  likely  to  crack  the  steel  than  fresh  water ; 
therefore,  as  the  water  wastes,  fresh  water  should 
be  added  to  it.  As  it  is  necessary  to  clean  the 
tank  out  occasionally,  it  would  be  well  before  using 
fresh  water  to  make  it  quite  hot,  by  putting  bars 
of  hot  iron  into  it  and  allowing  it  to  become  nearly 
cold  again  before  using  it,  or  the  chill  may  be 
taken  off  the  water  and  the  water  made  softer  by 
putting  some  ignited  charcoal  or  wood-ashes  into 
it.  It  is  obvious  that  the  colder  the  water  the 
more  effectually  it  hardens  the  steel,  and  the  more 

especially  when   the  steel  is  immersed  suddenly 
5 


106         HARDENING   AND   TEMPERING   OF   STEEL. 

and  a  rapid  movement  given  to  it  whilst  it  is  be- 
coming cool ;  but  when  fresh  cold  water  is  used 
there  is  always  greater  danger  of  the  steel  cracking. 
Brinish  liquids,  such  as  aquafortis,  urine,  or  water 
charged  with  common  salt,  etc.,  produce  rather 
more  hardness  than  plain  water  ;  but,  for  most  arti- 
cles, plain  water  with  the  chill  off  gives  sufficient 
hardness  to  the  steel.  Water  at  about  sixty  degrees 
measured  by  the  thermometer  is  the  most  suitable 
temperature  to  prevent  steel  cracking  in  hardening. 
Water  holding  soap  in  solution  prevents  the  steel 
from  hardening.  There  are  certainly  some  kinds 
of  tools,  also  some  pieces  of  work  used  in  machin- 
ery, which  require  to  have  a  greater  amount  of 
hardness  given  to  them  than  can  be  given  by  plain 
water ;  .there  are  some  kinds  of  gauges,  burnishers, 
and  certain  kinds  of  dies  which  require  to  be  very 
hard,  so  that  it  becomes  necessary  at  times  to  use  a 
saline  liquid ;  a  file  requires  also  to  have  a  nice 
hard  tooth.  When  steel  is  required  to  be  made  ex- 
tremely hard  it  may  be  quenched  in  mercury,  the 
chemists'  name  for  quicksilver ;  but  this  fluid  it  is 
obvious  can  only  be  used  on  a  small  scale. 

All  bright  articles  which  are  made  of  steel  and 
which  require  to  be  hardened  are  the  better  for 
being  heated,  previous  to  immersion,  in  contact 
with  carbon.  By  heating  steel  in  contact  with  car- 
bon, or  by  supplying  a  small  quantity  of  carbon  to 
the  surface  of  the  steel  after  it  is  heated,  it  favors 
the  steel  in  hardening ;  but,  though  it  is  better  to 
supply  a  small  quantity  of  carbon  to  the  surface 
of  the  steel,  still  it  is  not  absolutely  necessary  to  do 


HARDENING  AND  TEMPERING  OF  STEEL.    107 

so,  because  very  satisfactory  results  are  obtained 
with  some  kinds  of  articles  by  heating  them  in  red- 
hot  lead  previous  to  immersion.  When  red-hot 
lead  is  used  as  a  source  of  heat,  the  method  of  sup- 
plying carbon  to  the  surface  of  the  steel  cannot 
conveniently  be  adopted ;  neither  can  the  method  of 
supplying  carbon  to  the  surface  of  the  steel  be  con- 
veniently adopted  when  some  other  methods  of 
heating  steel  are  adopted,  such  as  heating  some 
small  steel  articles  between  the  heated  jaws  of  a  pair 
of  tongs,  or  between  two  heated  pieces  of  bar  iron,  or 
in  a  gas-flame,  the  flame  of  a  candle,  etc.  To  sup- 
ply carbon  to  the  surface  of  steel  articles,  the  arti- 
cles may  be  enclosed  in  a  sheet-iron  case  or  box, 
and  surrounded  on  all  sides  with  either  wood  char- 
coal or  aniflfal  charcoal ;  the  whole  will  require  to 
be  placed  in  a  furnace  or  hollow  fire  and  heated  to 
redness.  Wood  charcoal  is  too  familiar  to  every 
one  to  require  remark  in  this  place ;  but  it  may  be 
necessary  to  state  that  the  animal  charcoal  here 
spoken  of  is  nothing  more  than  any  animal  matter 
— such  as  horns,  hoofs,  skins,  or  leather,  etc.,  just 
sufficiently  burnt  to  admit  of  being  reduced  to 
powder.  If  it  is  found  more  convenient  to  heat 
the  articles  in  the  midst  of  the  ignited  fuel  of  an 
open  or  hollow  fire,  it  is  advisable  to  do  so ;  but 
when  any  bright  steel  article  is  heated  in  an  open 
or  hollow  fire,  free  of  wood  or  animal  charcoal,  it 
ought  always  to  be  coated  with  prussiate  of  potash, 
or  some  other  substance  which  will,  after  it  has  ar- 
rived at  a  red  heat,  protect  it  from  the  direct  action 
of  the  fire  and  water,  at  the  same  time  supplying 


108         IIAKDENING   AND   TEMPEEESTG    OF    STEEL. 

a  small  portion  of  carbon  to  the  surface  of  the  steel. 
Though  bright  steel  when  heated  in  the  midst  of 
the  ignited  fuel  of  a  hollow  or  open  fire  is  the  better 
for  being  coated  with  the  prussiate  of  potash,  still 
their  are  instances  when  it  will  be  advisable  not  to 
use  it;  for  instance,  if  the  potash  were  used  in 
hardening  saws  which  require  to  be  sharpened  with 
the  file  it  would  cause  greater  difficulty  to  file  them, 
consequently,  in  such  an  instance,  the  potash  should 
not  be  used.  When  it  is  required  to  coat  any  steel 
article  with  the  prussiate  of  potash,  the  article  will 
require  to  be  heated  to  redness  before  the  potash  is 
put  on  to  it,  otherwise  it  is  useless  to  put  it  on,  for 
the  steel  requires  to  be  sufficiently  hot  to  fuse  the 
potash  when  first  it  is  applied  for  the  potash  to  be 
of  any  practical  service  to  it.  The  potash  should 
always  be  finely  powdered  and  placed  in  a  small 
box,  the  lid  of 'which  should  be  full  of  small  holes, 
similar  to  a  grater  or  pepper-box.  The  reason  for 
this  is  that  it  is  the  most  economical  way  of  using 
it,  especially  if  the  article  is  held  over  a  piece  of 
plate  iron  whilst  the  potash  is  being  put  on  ;  what 
portion  of  the  potash  falls  upon  the  plate  must  be 
returned  to  the  box,  and  thus  prevent  it  being 
wasted. 

After  heating  any  steel  article  to  redness  and 
sprinkling  the'  potash  upon  it,  it  must  be  returned 
to  the  fire  for  a  few  minutes,  or  until  it  attains  the 
desired  heat;  the  article  is  then  ready  to  be  im- 
mersed in  the  water.  Sometimes  when  the  article 
is  very  large  it  is  necessary  to  draw  it  from  the  fire 
a  second  time  and  sprinkle  it  again  with  the  potash, 


HARDENING   AND   TEMPERING   OF    STEEL.         109 

in  order  to  give  it  a  thicker  coat  before  it  is  im- 
mersed in  the  water. 

Steel  which  is  hardened  with  the  skin  upon  it, 
will  undoubtedly  be  the  better  if  it  be  sprinkled 
with  the  prussiate  of  potash ;  for  it  has  always  a 
tendency  to  penetrate  through  the  thin  oxide,  and 
supply  carbon  to  the  surface  of  the  steel,  which, 
perhaps,  there  is  no  necessity  for  repeating,  is  favor- 
able to  the  steel  in  hardening. 

It  may  be  well  to  state  that  the  access  of  air  to 
the  potash  should  always  be  prevented,  when  the 
potash  is  not  in  use. 

Steel  in  the  state  it  leaves  the  forge,  with  the 
skin  or  thin  scale  upon  it,  is  less  liable  to  break  in 
hardening  than  steel  which  is  brightened  previous 
to  hardening.  The  skin  or  thin  scale  upon  the 
steel  prevents  the  water  from  acting  too  suddenly 
upon  the  steel ;  consequently  the  contraction  is 
slower.  Common  turning-tools  will  always  stand 
better ;  that  is,  they  will  keep  a  finer  and  firmer 
edge,  if  they  are  hardened  with  the  skin  upon  them, 
than  they  will  if  they  were  brightened  (either  by 
filing  or  grinding)  previous  to  hardening ;  in  fact, 
all  tools  that  can  be  ground  and  sharpened  upon 
the  grinding-stone  after  they  are  hardened,  will  be 
the  better  for  being  hardened  with  the  skin  upon 
the  steel ;  and,  if  properly  forged  by  the  tool-smith 
(who  is  generally  as  well  acquainted  with  the  prop- 
er shape  of  tools,  as  the  mechanic  who  uses  them), 
the  tools  will  require  very  little  grinding ;  and,  as 
for  water-cracks  in  the  steel,  there  will  be  none. 
When  turning-tools  are  made  of  the  best  cast  steel. 


110        HARDENING  AND   TEMPERING   OF   STEEL. 

and  hardened  previous  to  the  removal  of  the  skin 
or  scale,  and  which  are  not  intended  to  have  very 
keen  edges,  but  which  are  intended  to  sustain  a 
good  hard  edge  for  cutting  iron  and  other  metals 
(cast  iron  especially),  they  will  not  require  to  be 
tempered  after  being  made  hard,  but  the  heat 
should  be  carefully  regulated  at  first,  as  the  most 
useful  hardness  is  produced  by  that  degree  of  heat 
which  is  just  sufficient  to  effect  the  purpose ;  for  it 
is  quite  reasonable  to  suppose  that  the  hardness  of 
steel  depends  upon  the  crystallization,  and  the  in- 
timate combination  of  its  carbon ;  therefore,  the 
heat  which  effects  this  must  be  the  best. 

As  there  are  a  number  of  tools  used  in  the 
turnery  which  cannot  be  ground  upon  the  grinding- 
stone,  owing  to  their  peculiar  shapes,  it  becomes 
necessary  then,  whilst  the  steel  is  in  its  soft  state, 
to  fit  these  kinds  of  tools  up  with  the  file,  or  to  form 
them  in  the  lathe,  or  some  other  machine;  con- 
sequently these  kinds  of  tools  cannot  be  hardened 
with  the  skin  upon  them.  But,  as  there  is  greater 
liability  of  brightened  steel  breaking  in  hardening 
than  that  which  js  not  brightened,  and  as  some 
kinds  of  tools  cannot  be  ground  after  they  are  hard- 
ened, it  becomes  an  object  of  importance  that  they 
should  stand  well.  Therefore,  extra  precautions 
must  be  used  when  hardening  these  kinds  of  tools ; 
for,  were  their  cutting-edges  to  chip  through  being 
a  little  too  hard,  or  rub  off  through  being  a  little 
too  soft,  they  will  be  practically  useless  for  the  pur- 
pose they  are  intended  for,  until  they  have  been 
softened  and  fitted  up  again,  and  subsequently 


HARDENING   AND   TEMPERING   OF   STEEL.         Ill 

hardened.  In  some  instances  the  tools  would  be 
wholly  useless ;  this  would  be  the  case  with  screw- 
taps,  and  some  kinds  of  rimers,  broaches,  etc.,  for 
their  original  sizes  would  be  lost.  It  must  be  ob- 
vious, then,  that  if  extra  care  is  required  with  some 
kinds  of  tools,  it  must  be  with  those  kinds  which 
take  a  great  amount  of  labor  and  time  to  make 
them,  also  with  those  kinds  which  cannot  be  re- 
paired. 

It  is  well  known  that,  when  iron  is  heated  to  a 
high  temperature,  and  forged  upon  the  anvil,  a 
thick  unequal  scale  is  formed  upon  the  surface  of 
the  iron,  by  the  action  of  the  oxygen  of  the  atmos- 
phere ;  and  if  steel  is  heated  to  the  same  degree, 
and  forged  upon  the  anvil,  a  thick  unequal  scale  is 
formed  upon  its  surface  in  a  similar  manner  as  it  is 
formed  upon  the  surface  of  iron'.  This  thick  un- 
equal scale  would  cause  the  steel  to  harden  un- 
equally, if  it  were  not  removed  previous  to  hard- 
ening of  the  steel ;  but  it  must  be  borne  in  mind, 
that,  when  tools  are  made  of  the  best  cast  steel,  and 
forged  at  the  proper  heat,  and  the  anvil  kept  clean 
during  the  time  they  are  being  forged,  it  will  pre- 
vent this  thick  unequal  scale  being  formed  ;  but  a 
very  thin  equal  skin  or  scale  will  be  formed.  This 
thin  equal  scale  does  not  prevent  the  steel  from 
hardening  equally,  neither  does  it  prevent  the  steel 
becoming  sufficiently  hard  for  most  purposes  ;  but 
it  will  prevent  the  surface  steel  becoming  cool 
too  suddenly,  consequently  it  must  be  obvious  that 
it  will  have  a  tendency  to  prevent  the  steel  break- 
ing in  hardening. 


112    HARDENING  AND  TEMPERING  OF  STEEL. 

When  steel  is  required  to  possess  the  greatest 
possible  degree  of  hardness,  it  is  obvious  that  the 
scale  must  be  removed  previous  to  hardening  of  it. 

There  are  many  large  steel  articles  broken  after 
hardening  them,  by  taking  them  out  of  the  water 
before  they  are  thoroughly  cold ;  and,  perhaps,  a 
few  words  upon  this  will  not  be  out  of  place.  It  is 
the  opinion  of  many  mechanics  that  the  cause  of 
steel  breaking  after  it  is  lifted  out  of  the  water  is 
the  action  of  the  air  upon  the  steel,  when  first  the 
steel  comes  in  contact  with  the  air.  It  is  true  that 
large  masses  of  steel  frequently  break  immediately 
the  steel  is  lifted  out  of  the  water ;  but  I  am  at  a 
loss  to  see  in  the  slightest  degree  what  effect  the 
air  can  have  upon  the  steel  in  this  instance.  My 
opinion  is  this,  and  which  I  have  formed  from  ex- 
perience, that  if  the  steel  does  not  break  during  the 
time  it  is  becoming  cool,  there  is  no  more  danger  of . 
its  breaking  after  it  is  lifted  out  of  the  water  than 
what  there  was  of  its  breaking  in  the  water,  that  is, 
providing  the  steel  be  allowed  to  remain  in  the 
water  until  its  centre  becomes  quite  cool.  During 
the  time  the  steel  is  in  the  water  becoming  cool, 
and  after  a  certain  amount  of  heat  is  abstracted 
from  the  outer  crust,  there  is  a  peculiar  motion  or 
vibration  of  the  interior  particles  in  rearranging 
themselves  according  to  their  form.  This  peculiar 
motion  weakens  the  cohesion  of  the  particles.  The 
tension  of  the  steel  at  this  period  is  in  one  direction ; 
but  let  the  steel  be  lifted  out  of  the  water  before 
the  central  steel  has  become  quite  cool,  and  the 
tension  is  reversed  in  an  opposite  direction.  This 


HARDENING   AND  TEMPERING  OF   STEEL.         113 

is  caused  by  the  central  steel  imparting  heat  to  the 
inner  side  of  the  hardened  crust ;  and  this  sudden 
change  is  frequently  more  than  the  hardened  crust 
can  bear,  and  causes  the  steel  to  break.  If  the  steel 
does  not  break,  it  is  held  in  such  an  unequal  state 
of  tension,  from  the  particles  not  being  allowed  suf- 
ficient time  before  they  were  again  disturbed  to 
assume  the  exact  arrangement  to  which  they  are 
naturally  disposed,  that  the  tenacity  of  the  steel 
must  more  or  less  be  weakened.  It  is  not  requisite 
that  the  steel  should  lie  in  the  hardening  tank  until 
the  steel  and  the  water  become  quite  cool ;  for  in 
some  instances  the  steel  article  is  required  for  im- 
mediate use.  In  such  instances,  any  vessel,  such  as 
a  hand-bowl  or  a  water-bucket,  etc.,  may  be  sunk 
into  the  tank,  and  the  steel  article  or  articles  may, 
while  the  vessel  is  under  the  surface  of  the  water, 
be  lifted  into  the  vessel ;  after  which  the  vessel  can 
be  lifted  out,  with  as  much  water  in  it  as  will  cover 
the  article  or  articles.  The  vessel  may  then  be 
sunk,  with  the  article  or  articles  still  in  it,  into 
another  tank  of  quite  cold  water,  or  the  vessel  may 
be  placed  under  a  water-tap,  and  cold  water  run 
upon  the  articles ;  and  when  they  are  quite  cool 
they  can  be  lifted  out  with  safety.  It  will  be  ob- 
vious that  the  greater  the  mass  of  steel  the  greater 
the  risk  of  its  breaking  by  being  removed  from  the 
water  before  it  is  thoroughly  cold. 

There  are  many  articles  cracked  in  hardening 
by  heating  them  all  over,  or  throughout  their  body, 
and  then  partially  dipping  them,  into  the  water. 
All  kinds  of  articles  which  are  heated  all  over  are 


HARDENING  AND  TE&PERING   OF   STEEL. 

the  better  for  being  dipped  and  hardened  all  over ; 
and  then,  if  one  part  of  the  article  is  required  softer 
than  the  other  parts,  it  is  best  to  soften  it  after. 
To  spare  this  trouble,  at  the  same  time  lessen  the 
risk  of  fracture,  it  will  be  well  not  to  heat  some 
kinds  of  articles  in  any  other  part  but  that  which 
is  required  hard,  and  then  to  entirely  quench  them. 
The  heat  of  course  must  not  terminate  upon  the 
article  in  a  strict  line,  but  should  be  gradually 
tapered  off.  It  is  obvious  that  the  heat  will  not 
terminate  in  a  strict  line  when  the  article  is  heated 
in  a  common  smith's  fire ;  but,  when  red-hot  lead 
is  used  as  a  source  of  heat,  the  heat  upon  the  article 
is  liable  to  terminate  in  a  strict  line  unless  a  vertical 
movement  be  given  to  the  article.  If  only  a  cer- 
tain part  of  a  steel  article  is  required  to  be  hard- 
ened, and  the  article  be  heated  throughout  its  body, 
and  the  water  into  which  the  article  is  to  be  put  be 
quite  cold,  and  the  hardener  in  dipping  it  stop  at  any 
particular  part,  at  the  same  time  holding  it  quietly 
without  giving  it  a  movement  whilst  it  is  becoming 
cold,  there  is  always  great  danger  of  the  article 
cracking  at  the  very  spot  which  is  level  with  the 
surface  of  the  water;  and  sometimes  the  article 
will  break  asunder  at  that  particular  spot  as  evenly 
as  though  it  had  been  cut  with  a  saw.  The  tools 
required  by  the  millwright,  pattern-maker,  carpen- 
ter, joiner,  and  cabinet-maker,  are  those  kinds  of 
tools  which  are  generally  attended  with  the  greatest 
risk  by  being  heated  throughout  their  body,  and 
only  immersed  half  their  depth  into  the  water ; 
especially  the  small  and  middle-sized  varieties  of 


HAKDENING  AND  TEHPEKING  OF  STEEL.    115 

the  best  kinds,  which  are  always  made  wholly  of 
the  best  cast  steel,  and  which  are  generally  filed  or 
ground  bright,  and  fitted  to  shape  previous  to  hard- 
ening. The  tools  required  by  these  different  artists 
do  not  differ  so  much  from  each  other  in  construc- 
tion and  name  as  in  size,  though  tie  very  large 
tools  used  by  millwrights,  carpenters,  and  others 
for  heavy,  coarse  work  are  generally  composed  of 
iron  and  steel  welded  together,  the  steel  forming 
but  a  small  portion  of  the  whole  mass  of  metal. 
With  these  kinds  of  large  tools  there  is  less  risk 
of  fracture  in  hardening,  because  it  is  generally 
shear  steel  or  a  mild  kind  of  cast  steel  (steel  con- 
taining a  smaller  proportion  of  carbon)  which  is 
used  for  welding  to  the  iron.  It  is  obvious  that  if 
the  steel  be  properly  welded  to  the  iron,  a  flaw  will 
be  less  likely  to  occur,  and  a  rupture  more  difficult 
to  start. 

From  these  statements  the  reader  may,  perhaps, 
be  inclined  to  think  that  I  am  condemning  the 
method  which  is  so  much  practised  in  the  art,  that 
of  partially  dipping  the  articles  and  afterward  tem- 
pering of  them  by  the  heat  at  the  back  of  the  tool 
or  article ;  but  it  is  not  my  object  to  condemn  a 
method  which  I  know  from  experience  to  be  in  a 
considerable  number  of  instances  very  convenient 
and  very  economical ;  but  knowing  from  experience, 
that  certain  kinds  of  articles  are  so  liable  to  crack 
when  the  method  of  partially  dipping  them  is 
adopted,  I  have  made  it  my  object  to  state  the 
cause  of  their  cracking,  and  to  give  such  remedies 
as  will,  in  a  great  measure,  prevent  these  water 


116        HARDENING   AND   TEMPERING   OF   STEEL. 

cracks.  When  the  method  of  partially  dipping  a 
steel  tool  or  other  kind  of  article  is  adopted,  the  ar-' 
tide  may  generally  be  prevented  from  cracking  by 
simply  putting  the  water  in  motion  previous  to  dip- 
ping the  article,  or  by  giving  the  article  a  quick 
movement  when  it  is  in  the  water  as  far  as  it  is  re- 
quired hard ;  either  of  these  methods  will  prevent 
the  water  from  acting  so  evenly  in  cooling  it  in  a 
strict  line  ;  either  of  these  methods  causes  the  line 
between  the  hard  and  soft  part  of  the  article  to  oc- 
cupy more  space,  and  lessens  the  risk  of  fracture. 
"Water-cracks  may  also  be  prevented  in  that  part  of 
any  article  which  is  required  to  be  level  with  the 
surface  of  the  water,  by  simply  coiling  a  piece  of 
binding  wire  round  that  particular  part,  and  when 
sufficiently  heated,  coating  it  with  the  prussiate  of 
potash  previous  to  immersion.  This  method  pre- 
vents the  water  from  acting  so  suddenly  or  evenly 
upon  the  steel,  at  that  particular  part  of  the  arti- 
cle ;  consequently  it  prevents  it  cracking. 

Ohipping-chisels,  drills,  and  all  other  kinds  of 

/tools  which  are  only  partially  dipped  into  the  water, 
(  should  never  be  held  still  while  they  are  becoming 

J  cold  ;  but  they  should,  after  they  are  dipped  to  the 
required  depth,  have  a  sudden  vertical  or  other 
movement  given  to  them.  I  have  no  doubt  that 
many  have  noticed  when  they  have  been  chipping, 
that  their  chisels  have  sometimes  broken  off  about 
an  inch  or  rather  more  from  the  cutting-edge,  or  at 

O  O     7 

that  part  of  the  chisel  which  was  level  with  the  sur- 
face of  the  water  when  it  was  hardening.  The 
cause  of  the  chisels  breaking  in  this  particular  spot. 


HARDENING   AND   TEMPERING   OF    STEEL.          117 

arises  in  a  great  number  of  instances  from  the  chis- 
els having  been  held  quietly  in  the  water  when 
hardening.  The  water  cooling  them  across  in  a 
straight  line  causes  the  hardened  part  to  tear  from 
the  soft  part ;  and  the  chisels  sometimes  break  with 
a  very  light  blow  of  the  hammer,  and  sometimes  f 
with  the  very  first  blow.  I  have,  myself,  wit-  ' 
nessed  the  ends  of  drills  drop  off  by  simply  dabbing 
their  points  into  the  wooden  bench ;  I  have  also 
witnessed  the  ends  of  drills  drop  off  at  the  grind- 
ing-stone  when  they  were  being  sharpened,  after 
having  been  repaired ;  I  have  also  witnessed  the 
ends  of  drills  drop  off  on  the  slightest  application  to 
the  work ;  and  from  no  other  cause  but  from  the 
drills  having  been  held  quietly  in  the  water  when 
hardening.  But,  as  these  kinds  of  articles  are  gen- 
erally hardened  with  the  skin  on  the  steel,  they  are 
less  liable  to  break  than  articles  which  are  bright- 
ened previous  to  hardening.  I  recollect  once  hav- 
ing a  quantity  of  small  flat  drifts  to  harden,  which 
had  triangular  grooves  cut  in  them,  to  form  sharp 
cutting-edges,  something  similar  to  a  file,  but  cut 
coarser  and  deeper,  and  I  was  requested  to  leave 
the  top  part  of  them  (called  the  heads)  soft.  So  I 
put  a  certain  number  of  them  into  an  iron  box  and 
surrounded  them  on  all  sides  with  charcoal  dust ; 
after  luting  the  box  with  clay,  I  placed  it  in  a  hol- 
low fire  and  slowly  heated  the  whole  to  redness ; 
after  which,  I  opened  the  box  and  let  the  contents 
drop  from  the  box  into  the  water-tank,  with  the  in- 
tention of  subsequently  softening  the  heads.  After 
taking  them  out  of  the  water  and  examining  them, 


118         HAEDENING   AND   TEMPEKESTG   OF   STEEL. 

I  found  a  number  of  them  very  crooked  ;  this  was 
owing  to  their  being  so  slight  and  going  from  the 
box  so  suddenly  into  the  water.  As  these  kinds  of 
tools  are  required  for  clearing,  trueing,  and  finish- 
ing holes,  it  is  obvious  that  this  defect  of  being 
crooked  is  very  detrimental ;  for  these  tools  cannot 
produce  true  work  if  they  are  crookecl,  besides,  they 
are  more  liable  to  break  when  they  are  struck  with 
the  hammer  than  if  they  were  straight. 

As  the  above  method  did  not  afford  a  very  satis- 
factory result,  I  adopted  another  method.  I  placed 
a  certain  number  of  them  in  a  sheet-iron  pan  with- 
out a  lid  upon  it;  I  surrounded  the  drifts  with 
charcoal  dust,  the  same  as  previously,  and  heated 
the  whole  to  redness  in  a  hollow  £re ;  as  they 
became  heated  I  gripped  separately  the  head  of 
each  drift  with  the  pliers,  and  dipped  it  endways 
and  perpendicularly  and  slowly  into  the  water.  This 
method  had  the  effect  of  causing  them  to  keep 
straight  and  answering  the  purpose  so  far,  but  it 
took  a  longer  time  to  dip  them  separately;  so, 
thinking  to  save  this  extra  time,  I  thought  I  would 
only  dip  them  in  the  water  as  far  as  they  were 
required  hard,  and  that  would  save  the  time  and 
trouble  of  softening  the  parts  which  were  not 
(according  to  order)  to  be  made  hard,  namely, 
the  heads  of  the  drifts.  But  not  caring  about 
going  ahead  with  any  large  quantity  until  I  made 
myself  sure  that  all  was  going  on  well,  after  I  had 
dipped  about  two  dozen  of  them,  I  thought  it  ne- 
cessary to  examine  them,  and  I  did  not  find  one  of 
them  but  what  was  cracked  at  that  part  of  the  drift 


HARDENING   AND   TEMPEKING   OF   STEEL.         119 

which  was  level  with  the  surface  of  the  water  when 
hardening  them ;  so  I  dipped  the  remainder  of  them 
all  over,  and  separately,  and  hardened  them  through- 
out, and  not  a  crack  appeared  in  one  after.  After 
tempering  them  to  the  proper  temper,  I  made  some 
lead  red  hot  in  an  iron  ladle  and  dipped  the  heads 
that  were  to  be  soft  into  it,  and  accomplished  my 
object  very  nicely. 

This  tearing  of  the  particles  from  each  other 
when  the  hardening  terminates  in  a  strict  line  is  not 
at  all  times  sufficient  to  cause  the  steel  to  break 
asunder,  neither  is  it  at  all  times  sufficient  to  show 
signs  of  fracture ;  but  whether  the  steel  breaks 
asunder  or  not,  or  whether  there  are  signs  of  frac- 
ture or  not,  this  tearing  of  the  particles  from  each 
other  when  the  hardening  terminates  in  a  strict  line, 
must  always  with  highly  carbonized  steel  more  or 
less  take  place,  when  it  is  known  that  hardened 
steel  occupies  more  space  than  soft  steel,  and  that 
the  density  of  the  steel  is  different  in  the  two  states. 

When  it  is  required  to  harden  large  circular 
cutters  which  have  teeth  round  their  circumfer- 
ence, or  large  cutters  having  teeth  on  their  sides  as 
well  as  on  their  circumference,  or,  I  may  state,  such 
cutters  as  those  which  have  previously  been  treated 
of,  they  may  be  enclosed  in  a  sheet-iron  case  or  box 
and  surrounded  on  all  sides  with  either  wood  char- 
coal or  animal  charcoal.  The  box  will  require  to 
be  luted  with  clay  or  loam,  and  the  whole  placed  in 
a  furnace  or  hollow  fire  and  heated  to  redness.  A 
certain  amount  of  time  is  essential  to  allow  the  steel 
to  soak,  or,  in  other  words,  to  get  heated  uniformly 


120    HARDENING-  AND  TEMPERING  OF  STEEL. 

throughout.  After  the  cutters  are  properly  heated 
they  must  be  lifted  out  of  the  box  separately,  not 
by  the  tongs  or  pliers,  as  they  are  apt  to  spoil  the 
sharp  cutting-edges  of  the  cutter,  but  by  a  rod  of 
iron  (the  poker)  put  through  the  spin  die- hole  of 
the  cutter.  The  hardener  must  be  provided  with  a 
proper  tool  for  bearing  the  cutters  while  he  dips 
them  into  the  water,  as  the  pliers  do  not  answer  well 
for  this  purpose.  The  most  suitable  tool  for  dipping 
the  cutters  is  made  by  taking  three  pieces  of  round 
iron  about  one-quarter  of  an  inch  in  diameter  and 
three  or  four  inches  in  length.  Grip  the  thrqe 
pieces  at  the  end  with  the  tongs  and  weld  the  three 
opposite  ends  together,  after  which  the  welded  end 
must  be  scarfed  and  welded  to  the  end  of  another 
piece  of  iron  about  one-quarter  of  an  inch  in  diam- 
eter and  about  eighteen  inches  in  length ;  this  forms 
a  stem  with  three  prongs  at  one  end  of  it.  The 
three  prongs  must  be  turned  back  so  as  to  stand  at 
right  angles  with  the  stem ;  so  that  when  the  stem 
is  put  through  the  spindle-hole  of  the  cutter  and 
gripped  with  the  hand  the  cutter  will  lie  upon  the 
three  prongs.  A  kind  of  ring  or  loop  should  be 
turned  at  the  end  of  the  stem  to  keep  the  stem  from 
slipping  through  the  hand  by  the  weight  of  the  cut- 
ter, but  the  loop  must  be  sufficiently  small  to  pass 
through  the  spindle-hole  of  the  cutter. 

It  may  be  inquired,  will  not  a  long  bolt,  with  a 
large  flat  head,  answer  the  same  purpose  as  a  stem 
with  three  prongs  at  the  end  of  it  ?  The  answer  to 
this  is :  it  would  answer  quite  well  as  regards  the 
bearing  of  the  cutter,  but  the  large  flat  head  would 


HARDENING   AND   TEMPERING   OF   STEEL.         121 

prevent  the  water  from  passing  freely  through  the 
spindle-hole  of  the  cutter,  and  would  thus  prevent 
the  cutter  from  cooling  uniformly.  After  the  cutter 
is  lifted  out  of  the  box,  this  wire  stem  must  be 
put  through  the  spindle-hole  of  the  cutter  and 
gripped  with  the  hand ;  and  while  the  cutter  rests 
upon  the  three  prongs  it  must  be  immersed  into  the 
water,  and  instead  of  moving  the  cutter  backward 
and  forward  in  the  tank,  it  should  be  moved  up 
and  down  so  that  fresh  water  is  continually  passing 
through  the  spindle-hole  during  the  time  the  cutter 
is  becoming  cool.  The  deeper  the  tank  the  better 
it  is  for  the  purpose.  Care  must  be  taken  whilst 
moving  the  cutter  up  not  to  allow  it  to  come  above 
the  surface  of  the  water,  or  it  will  be  liable  to  crack. 
Should  the  tank  not  be  sufficiently  deep  to  allow 
moving  the  cutter  up  and  down,  the  cutter  may, 
after  it  is  beneath  the  surface  of  the  water,  be  turned 
sideways,  and  whilst  one  end  of  the  wire  stem  is 
gripped  with  the  right  hand  the  opposite  end  can 
be  gripped  with  the  left  .hand.  The  cutter  can 
easily,  whilst  it  is  beneath  the  surface  of  the.  water, 
be ?  shifted  toward  the  middle  of  the  wire  stem, 
which  will  keep  the  cutter  or  the  heated  water  as 
it  passes  through  the  spindle-hole  of  the  cutter 
from  burning  the  hands.  It  is  advisable  to  keep 
the  cutter  moving  until  it  is  sufficiently  cool  to  be 
gripped  with  the  hand.  If  more  than  one  cutter 
has  been  heated,  the  wire  stem  must  be  taken  out 
of  the  water,  as  it  will  be  required  for  dipping  the 
other  cutters.  There  is  no  necessity  for  removing 
the  first  cutter  from  the  water  until  all  the  cutters 
6 


122    HARDENING  AND  TEMPERING  OF  STEEL. 

that  have  been  heated  have  been  immersed ;  but, 
if  the  first  cutter  has  increased  the  temperature  of 
the  water  too  high,  more  cold  water  should  be 
added  to  it  before  the  second  cutter  is  immersed, 
and  so  forth,  if  necessary,  until  all  that  have  been 
heated  have  been  immersed.  The  cutters  may, 
after  they  are  hardened,  either  be  allowed  to  remain 
in  the  water  until  the  water  is  thoroughly  cold,  or 
they  may  be  lifted  out  of  the  water  by  the  method 
previously  explained.  If  the  cutters  are  uniformly 
heated  and  immersed  in  the  water,  in  the  manner 
just  described,  they  will  keep  their  proper  shape 
better  than  by  any  other  means ;  while  they  are 
much  less  liable  to  crack,  because  they  cool  more 
uniformly.  Any  size  cutters,  dies,  bushes,  rings,  or 
collars,  or  ring-gauges,  may  be  heated  and  immersed 
in  the  water  in  the  same  manner  as  circular  cut- 
ters. It  will  be  obvious  that  gauges  or  dies  which 
have  no  holes,  or  which  have  only  a  small  hole 
through  them,  cannot  be  dipped  with  the  same 
kind  of  tool  as  circular  cutters,  consequently  the 
pliers  will  be  quite  suitable  for  gripping  these  kinds 
of  articles.  It  is  not  absolutely  necessary  that  cir- 
cular cutters,  dies,  bushes,  rings,  gauges,  etc.,  should 
be  enclosed  in  a  box  to  heat  them,  neither  is  it  abso- 
lutely necessary  to  surround  them  on  all  sides  with 
wood  or  animal  charcoal,  as  it  will  answer  equally 
as  well,  and  be  a  far  more  expeditious  method,  to 
carefully  and  slowly  heat  them  in  the  midst  of  the 
fuel  of  a  hollow  fire  ;  but  when  these  kinds  of  arti- 
cles are  heated  for  hardening  in  the  midst  of  the 
fuel  of  a  hollow  fire,  they  should  always  be  coated 


HARDENING   AND   TEMPERING   OF    STEEL.         123 

with  the  prussiate  of  potash.  Dies  having  en- 
graved surfaces  are  undoubtedly  the  better  for  being 
heated  in  a  box  and  surrounded  with  wood  or  an- 
imal charcoal;  because  it  would  not  answer  very 
well  to  fill  the  fine  engraving  with  the  prussiate  of 
potash,  neither  would  it  answer  to  heat  them  in 
contact  with  the  air.  The  method  of  enclosing 
these  kinds  of  articles  in  an  iron  box,  and  surround- 
ing them  on  all  sides  with  wood  or  animal  charcoal, 
answers  three  good  purposes :  it  causes  the  heat  to 
be  very  slowly  and  equally  applied;  the  surfaces 
of  the  dies  are  rendered  rather  more  steelly  by  the 
absorption  of  carbon,  and  it  prevents  the  scaling  oc- 
casioned by  the  contact  of  the  air.  If  the  dies  or 
any  other  kind  of  steel  articles  be  previously  pol- 
ished, and  well  defended  from  the  air,  they  will  be, 
when  hardened,  nearly  as  clean  as  before.  Small 
cutters,  after  they  are  hardened,  require  to  be 
brightened  in  one,  two,  or  more  places,  and  tem- 
pered to  a  yellowish  white  or  light  straw  color.  A 
very  good  way*bf  applying  the  heat  for  tempering 
most  kinds  of  circular  cutters  is,  to  place  the  cutter 
upon  a  piece  of  round  bar  iron.  The  most  suitable 
piece  of  iron  for  the  purpose  is  made  by  slightly 
tapering  several  inches  of  a  piece  of  round  bar  iron. 
The  size  of  the  iron,  previous  to  drawing  the  taper 
upon  it,  should  be  a  little  larger  in  diameter  than 
the  diameter  of  the  spindle-hole  of  the  cutter ;  so 
that,  if  it  is  necessary  (whilst  tempering  the  cutter) 
to  draw  the  cutter  upon  the  stouter  part  of  the  iron, 
so  that  the  iron  may  fit  the  hole  tightly  and  supply 
more  heat,  it  may  be  done.  To  temper  the  cutters 


124         HARDENING   AND   TEMPERING   OF    STEEL. 

by  the  use  of  this  piece  of  iron,  the  tapered  end  of 
the  iron  will  require  to  be  heated  to  redness ;  it 
must  then  be  put  into  the  spindle-hole  of  the  cutter, 
the  iron  and  the  cutter  must  be  supported  with  the 
left  hand,  whilst  a  slow  rotary  motion  is  given  to 
the  cutter,  by  the  use  of  a  small  stick  of  wood, 
with  the  right  hand.  This  method  will  equalize 
the  heat,  and  cause  the  temper  to  be  more  uniform. 
As  soon  as  the  light  straw  color  appears  upon  the 
brightened  parts  of  the  cutter,  it  must  be  removed 
from  the  heat;  after  which  it  may  be  immersed 
either  into  water  or  oil,  or,  it  may  be  allowed  to 
become  cool  in  the  air,  for  it  matters  not  (after  it  is 
removed  from  the  heat)  which  way  it  becomes  cool 
— that  is,  providing  the  heat  has  not  been  too  sud- 
denly applied.  Though  this  is  the  most  suitable 
method  for  applying  the  heat  for  tempering  most 
kinds  of  circular  cutters,  still  there  are  some  kinds 
of  circular  cutters  requiring  to  be  tempered  after 
they  are  hardened,  where  it  will  be  found  more 
convenient  to  temper  them  upon  a  piece  of  flat  bar 
iron,  heated  to  redness.  The  heat  must  not,  in 
any  instance,  be  too  suddenly  applied.  It  is  ad- 
visable, in  some  instances,  when  tempering  some 
kinds  of  circular  cutters  upon  a  piece  of  flat  bar- 
iron,  to  place  a  piece,  of  cold  plate  iron  between  the 
cutters  and  the  red-hot  bar,  in  order  that  the  heat 
may  be  more  slowly  and  equally  applied.  It  will 
be  found  necessary,  when  tempering  some  kinds  of 
circular  cutters  upon  a  piece  of  flat  bar  iron,  to  turn 
them  over  occasionally  during  the  time  they  are  be- 
coming heated,  so  as  to  epxose  their  opposite  sides 


HARDENING   AND   TEMPERING   OF    STEEL.         125 

to  the  heat,  and  thus  impart  to  the  cutter  a  more 
uniform  temper.  The  yellowish  white  or  light 
straw  color  gives  tenacity  to  the  steel  without 
materially  reducing  its  hardness  ;  it  also  lessens  the 
risk  of  small  cutters  breaking  when  in  use.  There 
is  no  necessity  for  tempering  or  reducing  the  hard- 
ness of  the  largest  size  circular  cutters ;  because, 
owning  to  the  larger  body  of  steel,  they  are  much 
longer  than  the  smaller  size  cutters  in  becoming 
cool.  A  larger  quantity  of  steam  is  also  formed  at 
the  sides  of  the  large  cutters,  which  prevents  the 
water,  for  a  few  moments,  from  acting  upon  the 
steel ;  consequently,  the  largest  size  cutters  cannot 
become  so  hard  and  brittle  as  the  smaller  size  cut- 
ters. The  hardness,  of  course,  depends,  in  some 
measure,  upon  the  quality  of  the  steel;  likewise 
the  temperature  of  the  water  and  the  temperature 
of  the  cutters  when  they  are  immersed  in  the  water. 
If  the  quality  of  the  steel,  from  which  large  and 
small  cutters  are  made,  be  equal  and  if  the  temper- 
ature of  the  water  in  which  the  large  and  small 
cutters  are  immersed  be  equal  also,  and  if  the  large 
and  small  cutters  be  equal  in  temperature  when 
they  are  immersed,  this  variation  in  the  hardness 
of  the  largest  and  smallest  size  circular  cutters,  for 
the  reasons  just  given,  must  certainly  take  place. 
It  will  be  obvious,  then,  that  if  the  smallest  size 
cutters  require  only  to  be  reduced  in  temper  to  a 
yellowish  white  or  light  straw  color,  that  the  lar- 
gest size  cutters  will  not,  after  hardening,  require  to 
be  tempered  ;  but  the  hardening  strain  may  be  made 
more  uniform  throughout  the  body  of  large  cutters 
by  boiling  them  in  water  for  several  hours. 


126         HARDENING   AND   TEMPERING   OF   STEEL. 

Dies  which  have  engraved  surfaces,  after  they 
are  hardened,  require  to  be  tempered ;  not  because 
the  engraved  surfaces  of  the  dies  are  too  hard, 
but  because  the  whole  body  of  the  steel  requires  to 
be  toughened,  in  order  to  better  fit  the  dies  to  with- 
stand the  continual  hardship  to  which  they  are 
generally  exposed  when  in  use.  To  temper  these 
kinds  of  articles  the  engraved  surface  of  the  dies 
will  require  to  be  brightened ;  the  dies  must  then 
be  placed  upon  a  piece  of  flat  bar  iron,  several 
inches  of  which  must  be  heated  to  redness.  If  it  is 
required  to  temper  a  quantity,  several  may  be 
placed  at  once  upon  the  bar.  Care  must  be  taken 
that  all  the  dies  may  not  arrive  at  the  proper  tem- 
per at  the  same  moment.  The  dies  should  not  be 
placed  upon  the  hottest  part  of  the  bar  at  first ;  but 
they  should,  as  they  become  gradually  heated,  be 
pushed  upon  the  hotter  part  of  the  bar.  The  dies 
will  require  to  be  moved  occasionally  during  the 
time  they  are  becoming  heated  in  order  to  equalize 
the  heat.  As  soon  as  a  light  straw  color  appears 
upon  the  brightened  surface  of  the  dies,  they  must 
be  removed  from  the  hot  iron ;  and,  if  the  heat  has 
not  been  too  suddenly  applied  to  them,  they  may 
be  allowed  to  cool  in  the  air  of  their  own  accord. 
If  the  heat  has  been  too  suddenly  applied,  and  has 
changed  the  under  side  of  the  die  or  dies  to  a  deep 
blue  color,  it  will  then  be  requisite  to  cool  them 
either  in  water  or  oil,  otherwise  the  bottom  side  of 
the  die,  after  it  is  removed  from  the  hot  iron,  will 
continue  to  supply  heat  to  the  engraved  surface 
and  reduce  the  hardness  too  much ;  and  the  die  or 


HARDENING   AND   TEMPERING   OF    STEEL. 

dies  will  be  practically  useless  for  the  purpose  they 
are  intended  for,  until  the  operations  of  hardening 
and  tempering  of  them  have  been  repeated. 

Hardening  these  kinds  of  articles  a  second  time 
without  hammering  them  increases  the  risk  of  their 
breaking ;  and  as  they  cannot  be  hammered  with- 
out spoiling  the  engraving,  it  must  be  obvious  that 
very  great  care  is  required  when  hardening  and 
tempering  them,  and  the  hardener  ought  never  to 
place  more 'of  the  dies  upon  the  hot  bar  than  what 
he  can  conveniently  manage. 

When  it  is  required  to  harden  steel  rings  or  col- 
lars which  have  one  thick  edge  and  one  thin  edge, 
such  as  the  collars  of  some  turning-lathes,  these  may 
be  enclosed,  several  at  once,  in  a  sheet-iron  case  or 
box,  and  surrounded  on  all  sides  with  either  wood 
or  animal  charcoal.  The  box  will  require  to  be 
luted  with  clay  or  loam,  after  which  the  whole  may 
be  placed  in  a  furnace  or  hollow  fire,  and  the  steel- 
rings  or  collars  heated  to  the  proper  temperature 
suitable  for  hardening  them.  To  spare  the  trouble 
of  enclosing  these  kinds  of  articles  in  a  box  and  sur- 
rounding them  with  charcoal,  they  may  be  heated 
in  a  suitable  furnace  without  being  enclosed  in  a 
box,  or  they  may  be  heated  in  the  midst  of  the  fuel 
of  a  hollow  fire.  When  these  kinds  of  articles  are 
heated  in  a  furnace  or  hollow  fire  in  contact  with 
air,  and  the  fire  free  of  wood  or  animal  charcoal, 
they  should  always  be  coated,  previous  to  immer- 
sion, with  the  prussiate  of  potash,  in  the  manner 
previously  explained.  When  the  rings  or  collars 
arrive  at  the  proper  temperature  suitable  for  hard- 


128   HARDENING  AND  TEMPERING  OF  STEEL. 

ening  them,  they  must  be  drawn  from  the  fire  and 
placed  upon  the  same  or  a  similar  kind  of  wire  tool 
as  that  which  is  used  for  bearing  circular  cutters, 
whilst  they  are  becoming  cool  when  they  are  im- 
mersed in  the  water.  The  rings  or  collars  may  be 
immersed  in  the  water  separately,  or  two  or  three 
may  be  immersed  at  once,  by  taking  >care  to  place 
them  upon  the  wire  in  such  a  position  that  the 
stoutest  edge  of  each  ring  or  collar  may  enter  the 
water  foremost.  Previous  to  immersing  these  kinds 
of  articles  in  the  water,  and  when  it  is  intended  to 
place  two  or  three  of  them  at  once  upon  the  wire 
to  be  immersed  together,  it  will  be  necessary  to 
examine  the  depth  of  the  water  in  the  hardening 
tank,  in  order  to  ascertain  whether  the  depth  of  the 
water  is  sufficient  to  allow  the  rings  or  collars  when 
immersed  being  moved  up  and  down  without  risk 
of  bringing  a  part  of  the  uppermost  collar  above 
the  surface  of  the  water.  If  the  water  is  not  suffi- 
ciently deep  to  allow  these  kinds  of  articles,  when 
two  or  three  are  immersed  together,  being  moved 
sufficiently  to  remove  the  heated  water  from  the 
inside  of  them,  it  will  be  far  better  to  immerse  them 
separately,  and  thus  lessen  the  risk  of  their  break- 
ing. These  kinds  of  articles  require  to  be  very  slow- 
ly and  uniformly  heated,  and  should  not  be  plunged 
too  suddenly  into  the  water.  The  more  uniform 
the  temperature  the  less  liable  are  they  to  become 
oval  or  out  of  shape,  and  the  more  uniform  they 
become  cool  the  less  liable  are  they  to  crack ;  con- 
sequently it  must  readily  be  seen  that  these  kinds  of 
articles  require  to  be  immersed  very  slowly.  It  must 


HARDENING  AND  TEMPERING  OF  STEEL.    129 

also  readily  be  seen -that  it  is  quite  requisite  that 
the  thickest  edge  should  enter  the  water  toremost. 
The  degree  of  heat  required  to  harden  these  kinds 
of  articles  will,  of  course,  depend  upon  the  quality 
of  the  steel  from  which  they  are  made.  Sometimes 
rings  and  collars  are  made  of  the  best  cast  steel ; 
they  are  made  by  punching  a  long  hole  near  to  the 
end  of  a  steel  bar ;  after  the  hole  is  punched  a 
round  taper  mandrel  is  driven  into  it  to  widen  the 
hole ;  it  is  then  cut  off  the  bar  near  to  the  hole  and 
worked  upon  the  beak-iron  of  the  anvil.1;  When 
the  ring  or  collar  has  nearly  reached  the  proper 
form  and  size  it  is  finished  upon  a  larger  mandrel 
than  the  first,  after  which  it  is  annealed  and  turned 
in  the  turning-lathe  to  the  required  dimensions. 
"When  rings  or  collars  are  made  of  the  best  cast  steel 
by  the  method  here  explained,  they  will  only  re- 
quire to  be  heated  to  a  low  red  heat  to  harden 
them. 

Sometimes  rings  and  collars  are  made  of  shear 
steel.  They  are  made  by  scarfing  the  extreme  end 
of  a  bar  of  shear  steel ;  the  ring  or  collar  is  then 
partly  formed  by  bending  the  scarfed  end  of  the 
bar  round  the  beak-iron  of  the  anvil ;  the  partly- 
formed  ring  is  then  cut  off  the  bar,  and  the  second 
end  is  scarfed  ;  the  two  ends  are  then  brought  to- 
gether, and  united  by  welding.  The  shear-steel '' 
rings  are  then  finished  upon  a  mandrel ;  after  which, 
they  are  annealed  and  turned  in  the  lathe  to  the 
required  dimensions.  When  rings  or  collars  are 
made  of  shear  steel  by  the  method  here  explained, 
they  will  require  to  be  heated  to  a  bright  cherry- 


130    HARDENING  AND  TEMPERING  OF  STEEL. 

red  heat  to  harden  them.  Sometimes  rings  and 
collars  are  made  of  iron,  and  made  to  take  the  place 
of  steel ;  they  are  made  in  a  similar  manner  as  the 
shear-steel  rings  or  collars.  In  order  that  the  iron 
rings  or  collars  may  be  made  hard,  and*  take  the 
place  of  steel,  they  are,  after  they  are  finished  being 
turned  in  the  lathe  with  the  exception  of  polishing, 
case-hardened. 

It  is  seldom  necessary  to  temper  or  reduce  the 
hardness  of  steel  bushes,  rings,  or  collars ;  because 
the  generality  of  these  kinds  of  articles  are  required 
for  bearings  for  different  parts  of  machinery ,*where 
they  have  to  endure  a  great  amount  of  friction,  con- 
sequently they  require  to  be  very  hard  to  keep  them 
from  wearing.  King  and  plug  gauges,  which  are 
made  of  steel,  require  a  great  amount  of  hardness 
given  to  them  to  prevent  them  from  wearing ;  con- 
sequently these  kinds  of  articles  will  not,  after 
hardening,  require  to  be  tempered. 

Ring  and  plug  gauges  are  sometimes  made  of 
iron,  and  made  to  take  the  place  of  steel  by  being 
case-hardened,  previous  to  lapping  or  grinding  to 
their  proper  sizes.  The  method  of  case-hardening 
will  be  explained  in  a  subsequent  chapter. 

It  has  already  been  shown,  that  the  more  uni- 
formly steel  articles  become  cool  when  hardening, 
the  less  liable  are  they  to  fracture ;  and  it  has  been 
previously  recommended  that  the  stoutest  part  of 
steel  articles  should  enter  the  water  foremost.  It 
becomes  necessary,  perhaps,  to  state  here,  that  this 
method  of  immersing  steel  articles  cannot  in  all  in- 
stances be  adopted  ;  for  there  are  no  means  by  which 


HARDENING   AND   TEMPERING   OF   STEEL.         131 

the  stoutest  part  of  some  kinds  of  articles  can  be  made 
to  enter  the  water  foremost.  For  instance,  with 
such  an  article  as  a  feather-edge  circular  cutter  it  is 
not  practicable  to  get  the  stoutest  part  into  the 
water  first ;  consequently,  when  this  method  can- 
not be  adopted,  some  other  which  will  have  a  ten- 
dency to  cause  the  steel  to  cool  uniformly  must  be 
resorted  to.  It  will  be  obvious  that  the  method 
of  fitting  a  piece  of  flat  iron  to  the  thinnest 
part  of  this  kind  of  article  cannot  conveniently 
be  adopted.  The  process  of  concaving  the  sides 
to  reduce  the  substance  of  the  steel  in  that  part 
of  the  cutter  which  is  the  last  to  become  cool  can- 
not be  adopted,  because  this  would  unfit  a  feather- 
edge  cutter  for  the  purpose  for  which,  it  is  in- 
tended. It  is  evident  then,  that  if  none  of  these 
methods  can  be  adopted  with  a  feather-edge  circular 
cutter  that  there  is  great  risk  of  the  largest  kinds 
breaking  from  unequal  cooling.  When  it  is  required 
to  harden  a  large  feather-edge  circular  cutter,  it 
must  be  very  slowly  and  uniformly  heated  to  a 
cherry-red  heat ;  the  most  convenient  way  of  heat- 
ing it  is  in  the  midst  of  the  fuel  of  a  hollow  fire. 
As  soon  as  the  temperature  of  the  cutter  is  sufficient 
to  fuse  the  prussiate  of  potash,  it  must  be  taken  out 
of  the  fire  and  coated  with  the  potash,  and  then  be 
returned  to  the  fire  for  a  few  minutes,  or  until  it  ac- 
quires a  cherry-red  heat ;  after  which  it  must  be  drawn 
out  of  the  fire,  and  immersed  in  the  water  in  a  sim- 
ilar manner  as -other  kinds  of  circular  cutters.  It  will 
be  obvious,  from  previous  remarks,  that  if  the  tem- 
perature of  these  kinds  of  large  cutters  be  properly 


132    HARDENING  AND  TEMPERING  OF  STEEL. 

regulated  at  first,  they  will  not,  after  hardening,  re- 
quire to  be  tempered. 

Previous  to  putting  this  kind  of  cutter  into  the 
fire,  it  will  be  well  to  cut  out  two  rings  from  a  piece 
of  wire  cloth  and  bind  one  of  them  upon  each  side 
and  at  the  thin  part  of  the  cutter.  Several  short 
pieces  of  binding  wire  will  be  required  for  binding 
the  wire  rings  upon  the  cutter.  These  wire  rings 
will  not  prevent  the  thin  part  of  the  cutter  from 
hardening,  but  if  they  be  properly  bound  upon  the 
cutter  they  will  have  a  tendency  to  cause  the  potash 
to  cling  more  firmly  to  it  and  prevent  the  water 
from  acting  too  suddenly  upon  the  thin  part  of  the 
cutter,  thereby  causing  it  to  cool  more  uniformly. 
It  will  not  be  necessary  to  bestow  this  trouble  upon 
the  smaller  size  cutters  of  a  similar  shape ;  but,  with 
large  expensive  cutters,  to  lessen  the  risk  of  fracture 
is  not  labor  lost. 

It  occurs  to  me,  also,  that  the  use  of  the  wire 
rings  may  be  dispensed  with  by  taking  a  'certain 
portion  of  the  prussiate  of  potash  and  mixing  with 
it  a  certain  portion  of  flour  or  bean-meal,  or  some 
similar  substance,  and,  after  heating  the  cutter  to 
redness,  and  giving  it  one  coat  with  the  pure  prus- 
siate of  potash,  to  give  the  thin  part  of  the  cutter  a 
second  coat  with  the  mixture.  If  this  mixture  ad- 
heres to  the  thin  part  of  the  cutter  it  will  prevent 
the  water  cooling  it  too  suddenly,  and  thus  prevent 
the  cutter  breaking ;  but  I  have  never  given  this 
mixture  a  trial  myself,  and  cannot  speak  upon  its 
value  with  certainty. 

When  it  is  required  to  harden  an  eccentric  ring 


IIAEDENING  AND  TEMPERING   OF   STEEL.         133 

or  collar,  it  may  be  heated  in  the  midst  of  the  ig- 
nited fuel  of  a  hollow  fire.  If  it  is  made  of  the  best 
cast  steel  it  will  require  to  be  uniformly  heated  to 
a  cherry-red  heat  and  coated  with  the  prussiate  of 
potash  in  a  similar  manner  as  other  articles,  after 
which  it  must  be  immersed  endways  and  perpen- 
dicularly in  the  water  and  entirely  quenched.  It 
will  be  obvious  that  there  would  be  no  difficulty  in 
getting  the  stoutest  part  of  such  an  article  into  the 
water  foremost,  but  it  will  not  answer  to  adopt  this 
method  in  such  a  case.  If  the  stoutest  part  were 
to  enter  the  water  foremost  it  would  certainly  cause 
the  collar  to  cool  more  uniformly,  and  probably  it 
would  prevent  the  thinnest  side  of  the  collar  break- 
ing ;  but  then,  by  going  sideways  into  the  water,  it 
would  cause  the  hole  in  the  collar  to  become  oval, 
and  the  outside  of  the  collar  to  lose  its  proper  shape, 
which  would  unfit  it  for  the  purpose  for  which  it 
was  intended;  consequently  it  is  quite  requisite 
that  a  piece  of  iron  should  be  fitted  to  the  thin  side 
of  the  coilar  (as  has  previously  been  remarked),  and 
that  the  collar  should  be  immersed  endways  and 
perpendicularly  in  the  water. 

When  it  is  required  to  harden  a  large  piece  of 
round  cast  steel  in  which  a  hole  has  been  bored 
through  it  (such  a  piece  as  has  previously  be%n 
spoken  of),  it  may  he  surrounded  with  wood  or 
animal  charcoal  in  a  sheet-iron  box  and  heated 
either  in  a  furnace  or  a  hollow  fire  in  a  similar  man- 
ner as  other  articles,  or  it  may  be  heated  in  the 
midst  of  the  ignited  fuel  of  a  hollow  fire.  If  it  is 
heated  in  the  midst  of  the  ignited  fuel,  it  will  re- 


134:        HARDENING  AND   TEMPERING   OF   STEEL. 

quire  to  be  coated  with  the  prussiate  of  potash. 
Whichever  method  be  adopted  for  heating  it,  it  will 
require  to  be  heated  to  a  cherry-red  heat,  after 
which  it  must  be  withdrawn  from  the  fire  and  placed 
upon  the  same  kind  of  tool  as  that  which  is  used  for 
dipping  circular  cutters — it  must  be  immersed  end- 
ways and  perpendicularly  in  the  water.  During 
the  time  it  is  becoming  cool  it  must  be  moved  up 
and  down  in  the  water  in  order  to  allow  fresh  water 
to  pass  through  the  hole,  or,  in  other  words,  to  re- 
move the  heated  water  out  of  the  hole  ;  or  it  may, 
after  it  is  beneath  the  surface  of  the  water,  be  turned 
upon  its  side  and  drawn  backward  and  forward 
until  it  is  cool. 

It  may  be  inquired,  What  makes  the  difference 
whether  the  steel  be  moved  about  in  the  water  dur- 
ing the  time  it  is  becoming  cool,  or  whether  it  be 
held  still,  when  it  is  known  that  heated  water  al- 
ways rises  to  the  surface  ?  The  answer  to  this  is, 
that  the  heated  water  does  not  rise  to  the  surface  so 
suddenly  as  the  he^t  is  required  to  be  extracted 
from  the  inside  of  the  article ;  consequently,  it  is 
quite  requisite  that  it  should  be  moved  about  in  the 
water  in  order  that  the  cooler  portions  of  the  water 
may  pass  through  the  hole  and  cool  the  article  more 
uniformly. 

It  has  previously  been  stated  that  it  is  injurious 
to  bore  holes  too  near  to  the  outside  edges  of  steel 
articles  ;  but  it  is  obvious  that  boring  holes  near  to 
the  edges  cannot,  with  some  kinds  of  articles,  be 
avoided;  therefore,  if  the  hardener  is  required  to 
harden  any  kind  of  steel  article  which  has  holes  in 


HARDENING  AND  TEMPERING  OF  STEEL.    135 

it  near  to  the  edges,  it  is  advisable  before  putting 
the  article  in  the  fire  to  stop  the  holes  with  a  piece 
of  loam  :  this  method  will  prevent  the  steel  break- 
ing at  the  holes.  It  may  be  useful  to  some  who  are 
not  much  accustomed  to  harden  steel  to  know  that 
if  a  piece  of  binding- wire  be  wrapped  round  any 
part  of  a  steel  article,  and  a  piece  of  loam  wrapped 
round  the  wire,  it  will  prevent  the  steel  from  hard- 
ening in  that  part  when  it  is  immersed  in  the  water ; 
consequently  it  will  prevent  the  steel  breaking  at 
the  part  where  the  loam  is  on.  The  wire  is  for  no 
other  purpose  but  to  prevent  the  loam  from  falling 
off ;  the  loam  requires  to  be  dried  upon  the  article 
before  it  is  put  into  the  fire,  otherwise  it  will  prob- 
ably crack  and  let  the  water  get  at  the  steel.  But, 
for  the  sake  of  making  this  subject  properly  under- 
stood, as  it  may  often  prove  very  useful  to  the  hard- 
ener, let  us  suppose  that  the  middle  part  of  a 
piece  of  one  inch  square  cast  steel  is  required  to  be 
hardened  and  the  two  ends  required  to  be  kept  soft. 
We  will  suppose  it  to  be  four  inches  in  length,  and 
at  each  end  of  it  a  countersunk  round  hole,  for  the 
reception  of  a  bolt  three-eighths  of  an  inch  in  diam- 
eter, having  a  cheese-shaped  head  three-eighths  of 
an  inch  in  thickness,  and  three-quarters  of  an  inch 
in  diameter. 

It  must  easily  be  seen,  by  the  shape  of  this  kind 
of  article,  that  if  a  proper  method  is  not  adopted 
there  will  be  some  difficulty  in  hardening  it  to  make 
it  answer  the  requirement,  namely,  quite  hard  in  the 
middle  and  soft  at  the  ends,  and  not  cracked  at  the 
holes.  If  this  kind  of  article  could  be  made  hot  in 


136          HAEDENIKG    AND   TEMPEKINa   OF   STEEL. 

the  middle  without  heating  the  two  ends  there 
would  be  an  end  to  the"  difficulty ;  but  it  is  obvious 
that,  owing  to  the  shortness.of  this  kind  of  article, 
this  cannot  be  done,  so  that,  whatever  method  be 
adopted  in  heating  it  for  hardening,  it  will  require  to 
be  heated  throughout  its  body.  Fires  are  sometimes 
made  so  that  a  very  short  heat  may  be  got  upon  any 
part  of  some  kinds  of  articles  ;  but  this  is  an  article 
which  will  require  a  certain  amount  of  time  to  soak, 
consequently  the  middle  part  of  it,  cannot  be  prop- 
erly heated  in  a  short  open  fire  without  the  two  ends 
becoming  hot :  it  is  evident,  then,  that  .the  article 
must  be  heated  throughout  its  body.  There  are 
various  methods  that  could  be  adopted  in  hardening 
this  kind  of  article.  First,  it  may  be  heated  in  an 
iron  box  in  contact  with  charcoal,  or  it  may  be  heat- 
ed in  the  midst  of  the  ignited  fuel  of  a  hollow  fire ; 
wiien  it  .is  sufficiently  heated  it  may  be  lifted  out  of 
the  fire  with  the  pliers ;  one  end  of  it  must  then  be 
dipped  into  the  water  and  partially  "cooled,  after 
which  the  opposite  end  must  be  dipped  and  partial- 
ly cooled  in  a  similar  manner.  This  operation  is  to 
partly  cool  the  steel  to  keep  it  from  hardening  at 
the  parts  which  are  required  soft. 

"When  the  temperature  of  the  two  ends  is  re- 
duced beyond  that  which  will  harden  the  steel,  the 
whole  of  the  article  must  be  immersed  in  the  water 
and  entirely  quenched.  A  certain  amount  of  dexterity 
is  required  in  cooling  the  ends,  otherwise  the  middle 
part  of  the  article  which  is  required  hard  will  be- 
come too  low  in  temperature  to  harden  properly. 
By  adopting  this  method,  the  middle  part  of  the 


HARDENING  AND  TEMPERING  OF  STEEL. 

article  is  hardened  and  the  ends  remain  soft.  Still 
this  method  is  not  perfect ;  because  the  article  fre- 
quently becomes  cracked  at  the  holes  when  cooling 
the  ends. 

Another  method  of  hardening  this  kind  of  arti- 
cle is  to  heat  it  the  same  as  before,  and  immerse  it 
at  once  in  the  water.  This,  of  course,  hardens  the 
ends  as  well  as  the  middle.  The  ends  may  subse- 
quently be  softened,  though  very  imperfectly,  by 
placing  them  between  pieces  of  iron  heated  to  white- 
ness ;  or  the  heat  may  be  more  suddenly  applied  by 
punching  a  hole  (the  size  and  shape  of  the  end  of 
the  article)  in  two  separate  pieces  of  stout  iron,  and, 
after  heating  the  two  pieces  of  iron  to  a  whitish 
heat,  placing  the  ends  of  the  article  into  the  holes. 
This  method  of  hardening  this  kind  of  article  is 
not  perfect ;  because  the  article  is  liable  to  become 
cracked  at  the  holes  in  hardening,  and  the  hardness 
is  liable  to  become  reduced  in  the  middle  of  the 
articles  by  heating  the  ends  to  get  them  soft. 

Another  method  is  to  heat  the  article  in  a  hollow 
fire  and  harden  it  throughout,  after  which  the  two 
ends  may  be  made  soft  by  dipping  them,  one  at  a 
time,  in  some  red-hot  lead.  This  method  is  not  per- 
fect, because  the  article  is  liable  to  become  cracked 
at  the  holes  in  hardening,  and  too  much  time  is  re- 
quired for  heating  the  lead  for  softening  the  ends  ; 
and,  as  time  is  money,  this  becomes  a  very  expensive 
way.  Though  red-hot  lead  is  an  excellent  thing  for 
heating  some  articles,  .and  would  answer  quite  well 
for  softening  the  ends  of  this  kind  still  it  is  quite 
unnecessary  to  make  use  of  it  in  this  instance. 


138    HARDENING  AND  TEMPERING  OF  STEEL. 

The  most  convenient  and  satisfactory  method  of 
hardening  this  kind  of  article,  is  to  wrap  a  piece  of 
binding-wire  about  the  holes,  and  then  to  fill  the 
holes  with  loam,  at  the  same  time  cover  the  ends 
and  the  wire  with  the  loam  ;  this  will  form  a  small 
ball  of  loam  at  each  end  of  the  article  ;  the  wire  is 
to  prevent  the  loam  falling  off.  After  the  loam  is 
placed  upon  the  ends  it  will  require  to  be  gradually 
dried  before  it  is  put  into  the  fire ;  after  the  loam  has 
become  dry  the  article  may  be  placed  in  the  midst 
of  the  heated  fuel  of  a  hollow  fire ;  that  part  of  the 
article  which  is  not  covered  with  the  loam  will  require 
to  be  coated  with  the  prussiate  of  potash ;  the  potash 
may  be  put  on  without  drawing  the  article  out  of  the 
fire  by  using  a  slip  of  iron,  one  end  of  which  should 
be  the  shape  of  a  spoon ;  the  article  will  require  to 
be  heated  throughout  to  a  cherry-red  heat,  after 
which  it  must  be  drawn  out  of  the  fire  and  immersed 
in  the  water  and  entirely  quenched.  Those  parts  of 
the  article  which  are  surrounded  with  the  loam, 
namely,  the  holes,  will  remain  soft  and  will  not 
crack,  because  the  water  cannot  penetrate  through 
the  loam  quick  enough  to  harden  the  steel.  I  have 
myself  had  numbers  of  articles  to  harden  similar 
in  shape  to  the  one  just  described,  and  by  adopting 
the  method  of  stopping  up  and  surrounding  the 
countersunk  holes  with  the  loam  I  never  knew  one 
to  crack ;  though  I  have  seen  numbers  of  the  same 
kind  of  articles  cracked  at  the  holes  when  the  loam 
has  not  been  used.  It  may  be  imagined,  perhaps, 
that,  if  one  method  were  given  for  hardening  this 
kind  of  article  it  would  have  been  sufficient :  but  I 


HARDENING   AND   TEMPERING   OF    STEEL.         189 

have  thought  it  necessary  to  mention  various  meth- 
ods (at  the  same  time  I  have  stated  which  is  the  best 
method)  in  order  that  it  may  set  the  young  me- 
chanic thinking,  and  to  afford  him  a  better  oppor- 
tunity of  judging  for  himself  which  is  the  best 
method. 

It  has  previously  been  stated  that  sharp  inter- 
nal angles  are  unfavorable  to  articles  which  require 
to  be  hardened,  and  it  has  been  hinted  that  sharp 
internal  angles  should  be  avoided ;  but,  as  they  are 
required  in  some  kinds  of  articles,  and  as  they  are 
often  ]eft  in  articles  when  they  are  not  required  in 
them,  I  will  state  that,  when  I  have  an  article 
to  harden  which  has  sharp  internal  angles,  I  always 
bind  a  piece  of  binding-wire  in  the  angles  of  the 
articles,  and  when  I  have  a  circular  cutter  to  hard- 
en, which  has  a  flat  key- way  in  it  with  sharp  an- 
gles, I  always  make  a  kind  of  key,  by  bending  a 
piece  of  binding-wire  backward  and  forward  and 
then  bind  it  into  the  key- way  of  the  cutter.  This 
of  course  does  not  strengthen  the  cutter,  but  it  has 
a  tendency  to  cause  the  potash  to  cling  more  firmly 
at  the  key-way,  and  prevents  the  water  acting  too 
suddenly  upon  the  weakest  part  of  the  cutter.  It 
may,  perhaps,  be  thought  by  some  that  it  will  be 
better  to  fit  an  iron  key  into  it ;  if  an  iron  key  were 
fitted  tight  into  it,  it  would  have  a  tendency,  at  the 
period  when  the  cutter  was  shrinking  from  the  hot 
to  the  cold  state,  to  split  it,  as  the  cutter  would 
have  to  compress  the  key,  which  would  hold  it  for 
the  moment  in  a  greater  state  of  tension  (strain) 
than  if  the  key  were  not  there. 


14:0         HARDENING    AND   TEMPERING    OF    STEEL. 

It  has  previously  been  stated  that  it  is  injurious 
to  make  the  centres  too  deep  or  too  large  in  some 
kinds  of  articles  which  require  to  be  hardened ; 
consequently,  it  will  be  well  to  remark  here,  that, 
if  the  hardener  meet  with  articles  that  he  considers 
have  too  large. a  centre  in  them,  it  will  be  well  to 
stop  up  their  centres  with  a  piece  of  loam  previous 
to  hardening,  and  thus  prevent  them  becoming 
cracked  at  the  centres  in  hardening. 

When  it  is  required  to  harden  a  large  quantity 
of  small  or  medium  size  screw-taps  at  once,  they 
may  be  enclosed  in  a  sheet -iron  case  or  box,  and 
surrounded  on  all  sides  with  either  wood  charcoal 
or  animal  charcoal.  Preference  should  be  given  to 
the  wood  charcoal  on  account  of  it  undergoing  no 
change  by  being  exposed  to  heat,  providing  the 
access  of  air  is  prevented ;  consequently,  it  can  be 
saved  and  put  aside  to  be  used  again.  The  taps 
will  require,  of  course,  to  be  packed  in  alternate 
layers,  commencing  with  the  charcoal  on  the  bot- 
tom of  the  box,  to  the  thickness  of  about  three- 
quarters  of  an  inch,  and  finishing  with  a  layer 
about  the  thickness  of  the  first;  the  intermediate 
layers  of  the  charcoal  need  not  be  more  than  one- 
third  the  thickness  of  the  first  and  last  layers.  Suf- 
ficient space  must  be  left  every  way  for  the  expan- 
sion of  the  steel  taps  by  the  heat ;  otherwise,  as 
they  become  heated,  they  will  bend  and  damage 
each  other.  After  the  packing  is  completed  and 
the  lid  of  the  box  put  on,  it  will  require  to  be  luted 
with  clay  or  loam  (in  order  to  exclude  the  atmos- 
pheric air),  after  which,  the  box  and  its  contents 


HAEDENING   AND   TEMPERING   OF   STEEL.         141 

must  be  placed  in  a  suitable  furnace  or  hollow  fire, 
and  the  whole  heated  to  a  cherry-red  heat.  The 
fire  must  not  be  urged,  as  a  certain  amount- of  time 
is  essential  to  allow  the  contents  of  the  box  to 
become  uniformly  heated  throughout.  When  the 
whole  arrives  at  the  proper  heat,  the  box  may  be 
drawn  to  the  mouth  of  the  fire,  the  lid  removed, 
and  each  tap  taken  out  separately  and  immersed 
endways  (screw  end  foremost)  and  perpendicularly 
in  the  water ;  or  the  box  may  be  drawn  out  of  the 
fire,  and  the  whole  of  the  taps  immersed  at  once 
direct  from  the  box  in  the  water.  It  is  obvious 
that  it  is  a  more  expeditious  way  of  hardening  to 
immerse  them  all  at  once.  But  then  they  are  more 
likely  to  become  crooked  than  if  they  were  taken 
out  of  the  box  separately,  and  immersed  perpendic- 
ularly and  slowly  into  the  water.  If  the  harden- 
ing tank  is  made  of  iron,  and  the  method  of  im- 
mersing the  whole  of  the  taps  at  once  is  adopted,  it 
will  be  well  to  sink  a  piece  of  board  to  the  bottom 
of  the  tank  for  the  taps  to  fall  upon ;  the  board 
should  be  nearly  the  length  and  width  of  the  inside 
of  the  tank,  and  may  be  sunk  by  placing  a  piece 
of  iron  upon  each  end  of  it.  If,  in  addition  to  this, 
a  piece  of  iron  or  a  brick  be  placed  at  each  end,  be- 
neath the  board,  it  will  have  a  tendency  to  cause 
the  board  to  spring  and  scatter  the  taps  when  they 
are  tipped  out  of  the  box,  which  will  cause  them  to 
cool  more  equally.  The  taps  will  of  course  require 
to  be  packed  in  such  a  position  that  they  will, 
when  the  box  is  held  over  the  hardening  tank,  fall 
endways  and  perpendicularly  into  the  water. 


142         HARDENING   AND   TEMPERING   OF   STEEL. 

When  it  is  required  to  harden  a  large  quantity  of 
the  largest  size  screw-taps,  they  may  be  enclosed  in 
an  iron  box,  and  surrounded  with  carbon  in  a  simi- 
lar manner  as  the  smaller  sizes.  They  must  not, 
like  the  smaller  taps,  be  allowed  to  fall  direct  from 
the  box  into  the  water,  but  must  be  taken  out  of 
the  box  and  immersed  separately ;  but  it  will  be  a 
more'expeditious  way  to  heat  the  largest  size  taps 
in  the  midst  of  the  ignited  fuel  of  a  hollow  fire,  or 
a  suitable  furnace.  If  this  method  is  adopted,  the 
taps  will  require  to  be  very  slowly  heated;  but 
several  may  be  heated  at  once.  When  they  arrive 
at  a  cherry-red  heat,  which  is  the  heat  suitable  for 
hardening  them,  they  must  be  taken  out  of  the  fire 
separately  and  coated  with  the  prussiate  of  potash, 
after  which  they  must  be  returned  to  the  fire  for  a 
few  minutes,  Or  until  they  regain  the  heat  lost 
while  being  coated ;  after  which  they  must  be 
taken  out  and  immersed  endways,  screw  end  fore- 
most, and  perpendicularly  in  the  water.  This 
method  of  applying  the  heat  may  also  be  adopted 
with  small  quantities  of  small  or  middle-size  taps. 
Taps  hardened  by  this  method  will  answer  the  pur- 
pose for  which  they  are  intended  equally  as  well  as 
if  they  were  heated  in  a  box  surrounded  with  car- 
bon. 

In  all  cases  the  taps  must  be  allowed  to  remain 
in  the  water  until  they  become  quite  cool,  after 
which,  when  taken  out,  and  previous  to  using  them, 
they  will  require  to  be  tempered ;  but  before  tem- 
pering they  must  be  brightened  in  one,  two,  or  more 
places,  in  order  that  the  color  may  be  seen,  and  the 


HARDENING   AND  TEMPERING   OF   STEEL.         143 

proper  temper  ascertained.  It  will  not  be  necessary 
to  brighten  the  square  tops  or  heads,  but  only  the 
plain  round  parts  of  the  taps,  also  one  of  the  con- 
cave grooves  which  are  cut  along  the  side  of  the 
taps.  After  the  taps  are  brightened,  they  may  be 
tempered  by  exposing  them  again  to  heat.  When 
a  large  quantity  is  required  to  be  tempered,  place 
as  many  of  the  taps  at  once  as  may  be  convenient 
into  an  oven  or  gas-stove  specially  constructed ; 
heat  the  taps  until  a  dark  straw  color  appears  upon 
the  surface  of  them.  This  temper  is  the  best  that 
can  be  given  to  screw-taps  which  are  required  for 
general  purposes,  but  those  required  for  a  special 
purpose,  such  as  cutting  hard  cast  iron,  or  some 
kinds  of  steel,  will  then  require  to  be  tempered  to 
a  yellowish-white  or  light  straw  color.  As  soon  as 
the  proper  color  appears  upon  the  surface  of  the 
taps,  they  must  be  withdrawn  from  the  heat.  If 
the  color  does  not  further  change  after  the  taps  are 
withdrawn  from  the  heat,  it  is  a  proof  that  the  heat 
has  not  been  too  suddenly  applied ;  and  the  taps 
may  then  be  cooled  in  oil,  or  they  may  be  allowed 
to  become  cool  in  the  air  of  their  own  accord. 
Should  the  color  be  observed  to  be  changing  from 
a  straw  color  to  a  golden  color,  the  taps  must  in- 
stantly be  cooled  in  water ;  otherwise  they  will  be- 
^come  too  soft  for  the  purpose  for  which  they  are 
intended.  Cooling  the  taps  in  oil,  after  they  are 
tempered  to  the  proper  color,  has  a  tendency  to 
prevent  them  rusting  if  they  are  laid  aside.  The 
greater  portion  of  the  oil,  of  course,  will  require  to 
be  wiped  off;  but  the  taps  need  not  be  wiped  quite 


14:4        HARDENING   AND   TEMPERING   OF   STEEL. 

dry.  Another  method  by  which  screw-taps  may 
be  tempered,  is  to  place  a  piece  of  plate  iron  into 
and  near  to  the  mouth  of  any  common  furnace,  such 
as  those  which  are  connected  with  steam-boilers, 
etc.  After  the  plate  is  placed  in  the  furnace  several 
of  the  taps  may  be  placed  at  once  upon  the  plate, 
and  heated  until  the  proper  color  appears.  The 
taps  will  require  to  be  moved  about  upon  the  plate 
during  the  process  in  order  to  equalize  the  heat. 
As  they  become  heated,  and  the  proper  color  ap- 
pears upon  their  surfaces,  they  must  be  withdrawn 
from  the  heat ;  their  places  may  be  filled  up  with 
others,  and  a  continuance  of  the  process  may  be,  if 
necessary,  kept  up.  It  is  not  every  p.erson  who 
makes  screw-taps  that  has  large  quantities  to  tem- 
per at  one  time,  so  as  to  require  a  furnace,  or  oven, 
or  gas-stove.  The  amateur  mechanic  seldom  has 
more  than  two  or  three  sets  at  most  requiring  to  be 
tempered  at  one  time.  There  are  others  who  have 
only  a  few  to  temper  occasionally,  merely  for  the 
use  of  the  shop;  consequently,  it  may  be  well 
to  explain  another  convenient  method  whereby 
a  small  quantity  of  screw-taps  may  be  tempered 
without  the  use' of  the  furnace,  oven,  or  gas-stove. 
A  small  quantity  of  taps,  after  the'y  are  hardened 
and  brightened,  may  be  tempered  by  gripping  the 
top  of  the  taps,  one  at  a  time,  with  a  pair  of  tongs, 
and  holding  them  in  the  inside  of  an  iron  ring,' 
heated  to  redness,  until  a  dark  straw  color  appears 
upon  its  surface.  The  heated  ring  may  be  placed 
upon  the  anvil  or  other  suitable  place.  The  screw 
end  of  the  tap  must  be  allowed  to  project  out  of  the 


HARDENING    AND   TEMPERING    OF    STEEL.         145 

ring  when  first  the  heat  is  applied,  otherwise  the 
point  of  the  tap,  or  the  leading  thread,  will  change 
its  color  sooner  than  the  middle  part  of  the  tap,  and 
the  temper  will  be  unequal.     As  the  top  or  plain 
part  of  the  tap  changes  its  color,  the  screw  part 
must  be  drawn  back  into  the  ring.     If  the  jaws  of 
the  tongs  by  which  the  tap  is  gripped  be  previously 
heated  to  redness,  it  will  be  the  better,  as  the  heated 
tongs  will  help  to  supply  heat,  and  temper  the  taps 
more  uniformly.     It  will  be  obvious  that  if  the  top 
or  plain  parts  of  small  screw-taps  be  tempered  to  a 
blue,  that  they  will  be  less  likely  to  break  when  in 
use ;  consequently,  the  heated  tongs  will  be  very 
convenient  for  tempering  the  plain  parts  of  the  taps 
to  a  blue  at  the  time  that  the  screw  part  is  being 
tempered  to  a  straw  color.     The  hardener  ought  to 
be  provided  with  two  rings  and  three  pair  of  tongs, 
so  that,  whilst  one  heated  ring  and  one  pair  of 
heated  tongs  are  being  used,  the  other  ring  and 
another  pair  of  tongs  may  be  in  the  fire  becoming 
heated.     The  third  pair  of  tongs  .should  not  be 
heated,  but  they  should  be  ready  at  hand ;  so  that, 
if  it  should  happen  that  the  heated  tongs  supplied 
the  heat  too   suddenly  to  either  of  the  taps,  the 
heated  tongs  could  be  laid  aside  for  a  few  minutes, 
and  the  tap  gripped  with  the  cold  pair  of  tongs. 
With  care,  two,  and  sometimes  three  of  the  small- 
est or  the  middle  size  taps  may  be  tempered  with- 
out reheating  the  ring.     The  larger  the  diameter 
of  the  tap,  the  longer  it  will  be  in  changing  its 
color,  that  is,  providing  the  heat  is  properly  ap- 
plied.    The  thickness  of  the  iron  from  which  the 


146        HARDENING   AND   TEMPERING   OF   STEEL. 

ring  requires  to  be  made  must  be  in  proportion  to 
the  thickness  of  the  tap ;  or,  in  other  words,  the 
larger  the  diameter  of  the  tap  the  thicker  the  ring 
will  require  to  be,  in  order  that  the  ring  may  retain 
sufficient  heat  long  enough  to  temper  the  tap.  The 
diameter  of  the  inside  of  the  ring  will  require  to  be 
about  two  inches  larger  than  the  diameter  of  the 
tap.  If  smaller  than  this,  it  will  be  apt  to  supply 
the  heat  too  suddenly  to  the  tap.  The  length  of 
the  ring  will  require  to  be  about  the  same  length 
as  the  tap,  except  when  the  ring  is  required  for 
tempering  very  long  tapered  taps,  such  as  those 
sometimes  required  to  have  the  screw  part  as  much 
as  five,  six,  or  more  inches  in  length.  When  the 
ring  is  required  for  tempering  these  kinds  of  taps, 
it  will  be  more  convenient  to  have  it  somewhat 
shorter  than  the  tap,  and  move  the  tap  to  and  fro 
in  the  ring. 

The  hardener  will  find  in  practice  that  if  two 
or  three  short  rings  be  heated  and  placed  in  a  line 
with  each  other,  and  made  to  take  the  place  of  a 
long  single  ring,  it  will  be  more  convenient  for  tem- 
pering these  kinds  of  taps. 

Screw-taps  are  sometimes  required  for  some 
purposes  as  much  as  eighteen  and  more  inches  in 
length,  the  screw  part  occupying  but  a  small  por- 
tion (about  three  inches)  of  the  whole  length  of  the 
taps.  When  it  is  required  to  harden  these  kinds 
of  taps,  they  may  be  placed  in  the  midst  of  the 
ignited  fuel  of  a  very  small  hollow  fire ;  or  they 
may  be  placed  in  the  inside  of  a  piece  of  iron  pipe, 
the  iron  pipe  being  previously  placed  in  the  midst 


HARDENING  AND  TEMPERING  OF  STEEL.    14:7 

of  the  fuel  of  an  open  fire.  The  screw  part  of 
these  kinds  of  taps  is  the  only  part  which  requires 
to  be  hardened ;  consequently,  it  is  the  only  part 
necessary  to  be  heated.  They  must  be  very  slowly 
and  uniformly  heated  to  a  cherry-red  heat,  and  im- 
mersed endways  and  perpendicularly  in  the  water 
and  entirely  quenched.  These  kinds  of  taps  will, 
like  the  other  kinds,  require  to  be  brightened  and 
tempered.  The  plan  of  applying  the  heat  by  the 
use  of  an  iron  ring  will  be  very  convenient,  but  the 
method  of  gripping  the  taps  with  the  heated  jaws 
of  a  pair  of  tongs,  it  will  be  obvious,  cannot  con- 
veniently be  adopted ;  consequently,  if  they  be  stout 
taps,  a  very  thick  ring  heated  to  whiteness  will  be 
required.  The  whole  of  the  screw  part,  and  about 
one  inch  and  a  half  of  the  plain  part  of  the  tap, 
must  be  allowed  to  project  out  of  the  heated  ring, 
in  order  that  the  heat  may  be  applied  to  a  certain 
portion  of  the  plain  part  of  the  tap  first ;  otherwise 
the  tap  cannot  be  properly  tempered.  This  part 
of  these  kinds  of  taps  requires  to  be  in  contact  with 
a  greater  amount  of  heat  than  will  at  first  sight  be 
readily  imagined,  and  it  is  for  this  reason  that  I 
have  suggested  a  very  hot  ring.  If  the  diameter 
of  the  inside  of  the  ring  be  somewhat  smaller  for 
these  kinds  of  taps  than  for  other  kinds,  it  will  not 
be  amiss.  As  soon  as  this  part  of  the  tap  (which 
is  in  the  ring)  has  changed  its  color  to  any  of  the 
intermediate  colors  between  a  light  straw  and  a 
deep  blue,  the  screw  part  of  the  tap  which  is  now 
projecting  out  of  the  ring  must  be*  drawn  back  into 


148         HARDENING   AND    TEMPERING   OF   STEEL. 

the  ring,  and  tempered  to  the  same  color  as  other 
kinds  of  taps,  namely,  a  dark  straw  color. 

When  it  is  required  to  harden  master-taps  (com- 
monly called  by  workmen,  hobbs),  the  same  meth- 
ocls  adopted  with  other  kinds  of  taps  must  be  ap- 
plied, with  the  exception  that  these  kinds  of  taps 
must  be  left,  in  a  slight  .degree,  harder  than  the 
other  kinds.  The  reason  for  this  is,  they  are  mostly 
required  for  cutting  steel,  such  as  the  threads  of 
screw-dies,  also  for  cutting  the  threads  upon  those 
kinds  of  screw-tools  called  chasers,  etc. ;  conse- 
quently the  small  and  middle  size  master-taps  will 
not  require  to  be  reduced  in  temper  lower  than  a 
yellowish  white  or  light  straw  color.  It  will  be  ob- 
vious from  the  manner  in  which  master-taps  are 
grooved,  that  there  is  greater  liability  of  their  break- 
ing in  hardening,  and  less  liability  of  their  breaking 
when  in  use,  than  the  other  kinds  of  taps  of  the 
same  diameter ;  consequently,  when  it  is  required 
to  harden  the  largest  size  master-taps,  the  heat 
should  be  carefully  regulated  at  first,  so  that,  after 
they  are  immersed  in  water,  become  cool,  and  taken 
out,  they  will  be  ready  for  use,  and  thus  dispense 
with  the  subsequent  process  of  tempering.  The 
largest  size  master-taps  will  be  the  better  (whether 
heated  surrounded  with  carbon  in  an  iron  box,  or 
whether  heated  in  the  midst  of  the  fuel  of  a  hollow 
fire)  if  they  are  coated  with  the  prussiate  of  potash 
previous  to  immersion. 

When  it  is  required  to  harden  large  or  small 
screw-dies,  in  large  or  small  quantities,  they  may 
be  heated  in  a  similar  manner  as  screw-taps,  either 


HARDENING   AND   TEMPERING   OF    STEEL.         149 

by  enclosing  them  in  an  iron  box  and  surrounding 
them  on  all  sides  with,  carbon,  and  placing  the 
whole  in  a  furnace,  or  by  placing  them  in  the  midst 
of  the  ignited  fuel  of  a  hollow  fire.  Whichever 
method  is  adopted,  they  will  require  to  be  uniformly 
heated  to  a  cherry-red  heat.  They  will  require  to 
be  immersed  plain  end  foremost  in  the  water ;  or, 
in  other  words,  the  screw  part  of  the  dies  should  be 
uppermost  when  the  dies  enter  the  water.  It  will 
be  obvious  that,  if  the  dies  are  immersed  separately, 
there  will  be  .no  difficulty  in  making  the  plain  end 
of  them  enter  the  water  foremost ;  but  in  order  to 
approach  this  method  as  near  as  practicable,  the 
dies  should  be  packed  in  the  box  in  such-  a  position 
that  they  will  all  have  a  tendency  (when  the  box  is 
opened  and  held  over  the  water-tank)  to  fall  plain 
end  foremost  into  the  water.  When  the  dies  are 
heated  in  the  midst  of  the  ignited  fuel  of  a  hollow 
fire,  they  will  require  to  be  coated  with  the  prus- 
siate  of  potash  previous  to  immersion.  A  very 
convenient  box  in  which  to  heat  a  moderate  quan- 
tity of  small  screw-dies  or  small  screw-taps,  may 
be  made  by  welding  a  plug  into  the  end  of  a  piece 
of  large  wrought-iron  pipe.  A  loose  plug  will  be 
required  for  the  opposite  end  of  the  pipe;  it  must 
be  the  same  size  as  the  bore  of  the  pipe,  and  about 
one  inch  and  a  half  in  length.  Part  of  the  plug 
must  be  allowed  to  project  out  of  the  pipe  for  the 
convenience  of  gripping  it  with  the  tongs,  or  tap- 
ping it  with  the  hammer  when  required  to  be  taken 
out;  otherwise,  it  may  be  difficult  to  get  it  out, 
especially  after  it  has  been  luted  with  loam.  The 


150    HARDENING  AND  TEMPERING  OF  STEEL. 

plug  will  require  to  be  temporarily  fastened  into 
its  place ;  this  may  be  done  by  boring  a  hole  through 
the  pipe  and  the  plug,  and  driving  an  iron  pin 
through  the  two.  It  will  be  obvious  that  when  a 
large  quantity  of  screw-dies  or  screw-taps  are  re- 
quired to  be  heated  in  a  box,  the  box  should  be 
larger  in  proportion  to  the  quantity  to  be  operated 
upon,  and  the  box  will  require  to  be  made  of  plate 
iron. 

After  screw-dies  are  hardened,  they  will  require 
to  be  brightened  and  tempered.  The  tempering  may 
be  performed  by  placing  the  dies,  several  at  once, 
upon  a  hot  plate  of  cast  metal ;  or  they  may  be  tem- 
pered by  placing  them  upon  a  piece  of  bar  iron,  one 
end  of  which  must  be  heated  to  redness.  Those 
lands  of  dies  which  are  used  in  the  screwing  ma- 
chine, and  all  large  screw-dies  of  a  similar-  shape, 
will  require  to  be  placed  upon  the  heated  iron,  screw 
part  uppermost,  in  order  that  the  heat  may  not  be 
too  suddenly  applied  to  the  cutting  part  of  the  dies. 

As  soon  as  these  kinds  of -dies  are  observed  to 
be  changing  their  color,  they  must  be  moved  to  the 
cooler  part  of  the  iron,  otherwise  the  bottom  part  of 
the  screw  part  of  the  dies  will  be  apt  to  become  softer 
than  the  top  part,  and  the  temper  would  be  un- 
equal. It  will  sometimes  be  found  necessary,  after 
the  dies  are  removed  to  the  cooler  part  of  the  iron, 
to  turn  them  bottom  upward  for  a  few  moments,  or 
to  turn  them  upon  their  sides,  in  order  to  obtain  a 
uniform  degree  of  temper. 

Some  kinds  of  screw-dies  require  to  be  placed 
upon  the  hottest  part  of  the  iron  at  first,  and  as  they 


HABDENING   AND   TEMPEEING   OF    STEEL.         151 

become  heated  should  be  drawn  toward  the  cooler 
part  of  the  iron.  Other  kinds  of  screw  dies  require 
to  be  placed  upon  the  cooler  part  of  the  iron  at  first ; 
and,  as  they  become  heated,  they  require  to  be  drawn 
toward  the  hotter  part  of  the  iron.  This,  of  course, 
depends  upon  the  depth  of  the  dies,  or  the  distance 
between  the  screw  part  and  the  back  part  of  the 
dies. 

The  dies  must  be  allowed  to  remain  upon  the 
heated  iron  until  their  cutting  parts  become  uniform- 
ly changed  to  a  dark  straw  color ;  after  which  they 
may  be  cooled  in  water  or  oil,  or  allowed  to  cool  in 
the  air  of  their  own  accord,  according  to  circum- 
stances previously  explained.  The  smaller  size  screw- 
dies  may  be  uniformly  tempered,  and  the  heat  very 
gradually  applied,  by  placing  them  upon  a  stout 
piece  of  cold  plate  iron,  and  then  placing  the  plate 
and  dies  upon  a  thick  piece  of  iron  heated  to  a 
whitish  heat.  The  dies  must  be  turned  over  occa- 
sionally in  order  to  expose  all  their  sides  to  the  heat. 
As  their  surfaces  become  changed  to  a  dark  straw 
color,  they  may  be  pushed  off  the  plate  into  a  vessel 
containing  water  or  oil.  If  the  plate  has  not  become 
too  hot,  their  places  may  be  filled  up  with  others. 
If  the  plate  has  become  too  hot,  it  may  be  taken  off 
the  hot  iron  and  placed  upon  the  anvil  face ;  it  will 
then  in  a  few  moments  be  in  a  fit  state  for  temper- 
ing a  second  quantity.  By  putting  the  plate  back 
into  its  place  (upon  the  hot  iron)  a  third,  and  some- 
times a  fourth  quantity,  may  be  tempered  without 
reheating  the  iron. 

When  it  is  required  to  harden  a  large  quantity 


152        HARDENING   AND   TEMPERING   OF   STEEL. 

of.  those  kinds  of  screw-tools  called  chasers,  they 
may  be  placed  (several  at  once,  or  as  many  as  may 
be  convenient),  in  the  midst  of  the  ignited  fuel  of  an 
open  fire,  or  they  may  be  placed  in  the  midst  of  the 
ignited  fuel  of  a  very  small  hollowfire.  The  screw  end 
or  cutting  part  of  the  chasers  requires  to  be  heated  to 
a  cherry-red  heat.  The  blast,  of  course,  must  be  spar- 
ingly used..  When  they  arrive  at  the  proper  heat,  they 
must  be  drawn  out  of  the  fire ;  but,  should  there  be 
some  in  advance  of  the  others,  these  must  be  the 
first  to  be  drawn  out,  after  which  the  heated  end 
will  require  to  be  coated  with  the  prussiate  of  pot- 
ash.^ They  must  then  be  returned  to  the  fire  for  a 
few  minutes,  or  until  they  acquire  a  cherry-red  heat, 
after  which  they  must  be  immersed  into  the  water 
and  entirely  quenched.  In  order  to  keep  up  a  con- 
tinuance of  the  process,  as  they  are  withdrawn  their 
places  in  the  fire  must  be  filled  up  with  others. 
After  the  whole  of  them  have  been  immersed  and 
become  cool,  they  will  require  to  be  brightened  and 
tempered.  They  may  be  brightened  upon  a  grind- 
ing-stone  or  an  emery-wheel,  or  by  rubbing  the  top 
surface  with  a  piece  of  grin  ding-stone,  or  by  an 
emery  stick,  or  a  piece  of  emery  cloth.  After  the 
chasers  are  brightened  they  may  be  placed,  several 
at  once,  upon  a  piece  of  flat  bar  iron  heated  to  red- 
ness. The  screw  end  of  the  chasers  must  be  allowed 
to  project  some  distance  (about  one  inch  and  a 
quarter)  over  the  heated  iron,  otherwise  the  heat 
will  be  too  suddenly  applied  to  the  cutting  parts  of 
the  chasers.  As  soon  as  a  yellowish-white  or  light 
straw  color  appears  upon  the  cutting  parts  of  the 


HARDENING   AND   TEMPERING    OF   STEEL.          153 

chasers,  they  must  be  removed  from  the  heat  and 
cooled  in  water  or  oil,  otherwise  the  back  part  of 
the  chasers  which  was  in  contact  with  the  heated  iron 
will  continue  to  supply  heat,  and  the  chasers  will 
become  too  soft.  As  the  chasers  are  removed  from 
the  hot  iron,  their  places  can  be  filled  up  with  oth- 
ers. By  having  two  pieces  of  iron,  one  piece  in  the 
fire  becoming  heated  whilst  the  other  piece  is  being 
used,  a  continuance  of  the  process  may  be  kept  up. 
After  the  chasers  are  taken  out  of  the  water  or  oil, 
and  the  top  surface  ground  upon  the  grinding-stone, 
they  are  ready  for  use.  Though  this  method  is  a 
very  expeditious  one  for  hardening  and  tempering 
a  large  quantity,  still  it  is  not  absolutely  necessary 
to  adopt  it  with  a  small  quantity,  or  a  single 
chaser ;  because  they  may  with  care  be  hardened 
and  tempered  equally  as  well  by  heating  them 
and  partially  dipping  them  into  the  water  and 
tempering  them  by  the  heat  at  the  back  part  of  the 
chaser,  without  the  use  of  the  hot  iron.  It  will  be 
obvious  that,  when  this  method  is  adopted,  a  great- 
er portion  of  the  tool  will  require  to  be  heated,  in 
order  that  the  back  part  of  the  chaser  may  retain 
sufficient  heat  to  temper  the  cutting  part  after  it 
has  been  immersed  into  the  water. 

When  this  method  of  partially  dipping  the 
chaser  is  adopted,  it  will  be  advisable  to  put  the 
water  in  motion  previous  to  dipping  the  chaser ;  or, 
otherwise,  when  the  cutting  part  of  the  chaser  is 
beneath  the  surface  of  the  water,  give  the  chaser  a 
quick  movement ;  this  will  prevent  the  water  from 
cooling  the  steel  in  a  strict  line,  and  guard  against 


154:         HARDENING   AND   TEMPERING    OF    STEEL. 

water-cracks.  That  part  of  the  chaser  which  is  be- 
neath the  surface  of  the  water  must  be  allowed  to 
remain  in  the  water  until  it  becomes  quite  cool, 
after  which  it  must  be  taken  out  and  brightened. 
In  a  short  time  the  back  part  of  the  chaser  will 
supply  sufficient  heat  to  the  cutting  part  to  temper 
it  to  the  desired  color.  As  soon  as  the  proper  color 
appears,  the  chaser  must  be  entirely  quenched; 
and,  when  taken  out  of  the  water  and  ground  upon 
the  grinding-stone,  it  will  be  like  those  which  have 
been  wholly  quenched  and  subsequently  tempered 
on  the  heated  iron,  ready  for  use. 

When  it  is  required  to  harden  a  screw-plate,  it 
may  be  placed  in  the  midst  of  the  ignited  fuel  of  a 
very  small  hollow  fire,  or  among  the  ignited  fuel 
of  an  open  fire.  '  It  well  require  to  be  very  slowly 
and  uniformly  heated  to  a  cherry-red  heat ;  the 
blast  of  course  must  be  sparingly  used,  otherwise  it 
will  become  crooked.  There  is  no  necessity  for 
heating  the  whole  length  of  the  shank  or  handle ; 
bul  it  is  quite  necessary  to  heat  a  small  portion  of 
it,  in  order  to  obtain  a  more  uniform  heat  upon  the 
plate.  As  soon  as  the  temperature  of  the  plate  is 
sufficient  to  fuse  the  prussiate  of  potash,  it  must  be 
withdrawn  from  the  fire,  and  coated  with  the  pot- 
ash, in  a  manner  similar  to  other  kinds  of  tools ; 
after  which  it  must  be  immersed  very  slowly,  end- 
ways and  perpendicularly,  in  water.  The  largest 
size  screw-plates  will  generally  keep  truer  by  being 
immersed  edgeways  and  horizontally  in  the  water. 
The  screw-plate  must  be  allowed  to  remain  in  the 
water  until  it  becomes  quite  cool,  after  which, 


HARDENING   AND   TEMPERING   OF    STEEL.         155 

when  taken  out,  it  will  require  to  be  brightened 
and  tempered.  It  may  be  tempered  by  holding  it 
over  a  piece  of  flat  bar  iron  (heated  to  redness), 
until  a  dark  straw  color  appears  upon  its  surface ; 
or  it  may  be  tempered  between  two  pieces  of  flat 
iron  heated  to  redness,  and  placed  a  certain  distance 
apart  from  each  other,  in  order  that  the  heat  may 
not  be  too  suddenly  applied ;  or  it  may  be  held  in 
the  inside  of  an  iron  ring  heated  to  redness ;  or  it 
may  be  tempered  in  a  sand-bath,  provided  the  tem- 
perature of  the  sand  is  just  sufficient  to  change  it 
to  the  proper  color — if  the  sand  is  hotter  than  this, 
there  is  a  great  risk  of  the  threads  becoming  too 
soft ;  or  the  heat  may  be  applied  by  any  other  con- 
venient method,  after  which  the  plate  will  be  ready 
for  use. 

Screw-plates  and  screw-dies  are  often  ruined  by 
being  used  upon  iron  and  steel  rough  from  the 
forge,  and  covered  with  scales,  which,  from  their 
hard,  gritty  nature,  grind  away  the  threads.  In  all 
cases  the  rough  scale  should  be  removed  from  the 
iron  or  steel,  either  by  the  turning-tool,  file,  or 
grin  ding-stone,  previous  to  screwing  it  with  the 
screw-plate  or  the  dies.  It  is  not  an  uncommon 
practice  with  some  workmen,  after  they  have  fin- 
ished forging  a  piece  of  iron-work,  and  whilst  the 
iron  is  at  a  red  heat,  to  immerse  it  in  water  and 
partly  cool  it,  with  a  view  of  giving  the  work  a 
cleaner  appearance;  but  this  is  a  very  bad  cus- 
tom, especially  when  the  forging  requires  to  be 
screwed.  It  very  often  happens  that  the  iron 
contains  veins  of  steel,  which  harden  by  immer- 


156        HARDENING   AND   TEMPERING-   OF   STEEL. 

sion ;  and,  though  the  metal  may  not  be  so  hard 
as  to  prevent  its  being  cut  with  a  hard  turning- 
tool,  still,  when  it  comes  to  be  screwed  with  the 
stocks   and    dies,  or    with   the  dies   belonging  to 
the   screwing-machine,   or  with    the    screw-plates 
(which  tools  are  always  less  hard  than  the  turning- 
tools),  it  will  spoil  the  dies  or  the  screw-plates; 
and  because  this  hard  place  or  places  do  not  happen 
to  be  detected  when  turning  the  work  (on  account 
of  using  a  very  hard  tool),  the  steel  the  dies  or 
screw-plate  is  made  of  will  be  thought  bad,  or  badly 
tempered.     The  fact  is,  the  work  should  always  be 
annealed  rather  than  hardened.     In  all  cases  when 
an  impure  iron  is  made  use  of  for  forgings,  and 
which  will  subsequently  require  to  be  screwed, 
either  with  the  screw-dies  or  the  screw-plate,  or 
which  may  require  to  be  cut  with  circular  cutters 
or  with  circular  saws,  the  forgings  should  always 
be  annealed  previous  to  leaving  the  smithy.     The 
forgings,  of  course,  will  be  the  better  for  being  an- 
nealed supposing  they  are  to  be  screwed  with  the 
screw-tools  belonging  to  the  turning-lathe ;  though 
it  is  not  of  so  much  importance  as  when  they  are  to 
be  screwed  with  the  dies,  or  the  screw-plate,  or  cut 
with  circular  cutters,  or  circular  saws,  because  the 
screw-tools  belonging  to  the  turning-lathe  can  be 
ground  again,  provided  they  chip  from  being  very 
hard ;  whereas,  the  generality  of  screw-dies,  screw- 
plates,  and  circular  cutters,  and  even  circular  saws, 
when  very  hard,  and  once  spoilt,  will  not  admit  of 
being  again  sharpened,  but  will  be  practically  use- 
less, until  they  have  been  annealed,  and  cut  up 


HARDENING   AND   TEMPERING   OF    STEEL.         157 

again,  and  subsequently  hardened.  Annealing 
makes  the  iron  more  uniform  in  temper,  and  will 
save  much  subsequent  trouble ;  it  will  greatly  fa- 
cilitate the  work  when  fitting  it  up. 

When  it  is  required  to  harden  a  large  quantity 
of  stout  circular  saws  at  once  (for  cutting  metals), 
they  may  be  enclosed  in  a  sheet-iron  case,  or  box; 
they  will  require  to  be  surrounded  on  all  sides  with 
either  \vood  or  animal  charcoal.  Sufficient  space 
must,  of  course,  be  left  every  way  for  the  expansion 
of  the  saws ;  otherwise  they  will  become  buckled  in 
heating.  After  the  saws  are  enclosed  and  the  box 
luted  with  clay  or  loam,  the  whole  may  be  placed 
in  a  suitable  furnace  or  liollow  fire  and  the  saws 
heated  to  a  cherry-red  heat  (the  fire  of  course  must 
not  be  urged.)  As  soon  as  the  whole  arrive  at  the 
proper  uniform  temperature,  the  box  must  be  drawn 
toward  the  mouth  of  the  fire,  the  lid  taken  off  and 
the  saws  taken  out  separately.  They  may  either  be 
taken  out  of  the  box  with  the  pliers  or  by  a  small 
rod  of  iron,  having  a  small  hook  turned  upon  one 
end  of  it.  The  saws  will  require  to  be  immersed 
edgeways  in  a  trough  containing  water,  the  surface 
of  which  must  be  covered  with  a  film  of  oil.  The 
oil  will  float  of  itself  upon  the  surface  of  the  water 
and  burn -upon  the  saw  as  it  passes  through  it. 
The  burnt  oil  forms  a  coating  of  coal  upon  the  saw, 
which  protects  it  from  the  direct  action  of  the  water, 
and  lessens  the  risk  of  fracture. 

Though  saws  are  the  better  for  being  enclosed  in 
a  box  and  surrounded  with  charcoal  when  heating 
them,  still,  when  a  single  saw  is  required  to  be 


158    HARDENING  AND  TEMPERING  OF  STEEL. 

hardened  in  a  hurry,  it  will  be  more  expeditious  to 
place  it  upon  a  piece  of  cold  sheet  iron,  and  then  to 
heat  the  iron  and  the  saw  in  the  midst  of  the  ignited 
fuel  of  a  hollow  tire ;  and  when  it  arrives  at  the 
proper  temperature,  it  must  be  taken  off  the  plate 
and  immersed  in  the  hardening  fluid.  By  placing 
the  saw  upon  a  piece  of  cold  sheet  iron,  it  causes 
the  heat  to  be  very  slowly  applied,  and  it  has  a  ten- 
dency to  prevent  the  saw  buckling  in  heating.  Oil 
alone,  or  oil  in  which  tallow  has  been  dissolved,  is 
sufficient  to  give  the  thinnest  kinds  of  saws  a  suffi- 
cient degree  of  hardness ;  but  those  of  a  medium 
thickness  are  the  better  for  being  hardened  in  solid 
tallow  (the  saws  may  be  placed  separately  between 
two  flat  lumps  of  tallow).  Tallow  differs  from  oil  in 
the  absorption  of  heat  for  its  fusion ;  consequently, 
a  more  considerable  degree  of  hardness  is  given  to 
the  steel  by  the  tallow  than  by  the  oil ;  besides,  it 
hardens  the  steel  to  a  greater  depth  than  oil.  Yery 
thin  blades  of  steel  may  be  made  sufficiently  hard 
for  some  purposes  by  heating  the  blades  to  a  red 
heat  and  then  placing  them  between  two  heavy 
surface  plates ;  the  surface  plates  will  be  better  if 
they  be  smeared  with  tallow,  previous  to  putting 
the  blade  between  them.  When  the  saws  are  re- 
moved from  the  hardening  trough,  they  are  general- 
ly brittle  and  warped ;  consequently,  they  will  re- 
quire to  be  tempered  and  hammered  flat.  The 
tempering  may  be  performed  in  a  variety  of  ways, 
depending  of  course  upon  the  size,  shape,  and  quan- 
tity. Circular  saws,  which  are  required  for  sawing 
hard  substances  (such  as  iron  or  steel),  and  which 


HARDENING  AND  TEMPERING  OF  STEEL.    159 

have  a  round  spindle-hole,  about  one  inch  in  diam- 
eter in  them,  will  require  to  be  tempered  to  a  light 
straw  color.  These  may  be  tempered  by  first  bright- 
ening their  surfaces,  and  then  placing  them  upon  a 
piece  of  hot  iron.  The  piece  of  iron  which  will  be 
required  for  tempering  these  kinds  of  saws  may  be 
made  by  the  following  method.  Take  a  piece  of 
round  bar  iron,  one  inch  in  diameter  and  eight  or 
nine  inches  in  length  ;  heat  one  end  of  it  and  ham- 
mer it  so  as  to  make  it  fit  into  the  small  square  hole 
in  the  anvil ;  at  the  opposite  end  of  this  piece  of  iron, 
and  at  about  two  inches  from  the  extreme  end,  weld 
a  moderate-sized  iron  collar ;  the  collar  should  be 
made  of  half  round  iron,  so  that  it  will,  after  it  is 
welded  upon  the  piece  of  round  bar,  form  a  large 
lump,  the  shape  of  a  round  ball.  The  object  of 
this  large  lump  is  to  retain  the  heat  for  a  considera- 
ble time,  so  that  several  of  the  saws  may  be  tem- 
pered before  the  iron  will  require  to  be  reheated. 
If  two  of  these  lumps  were  made,  one  of  them 
could  be  in  the  fire  becoming  heated,  whilst  the 
other  lump  is  being  used  ;  so  that,  if  it  were  neces- 
sary, a  continuance  of  the  process  may  be  kept  up. 
The  object  of  having  this  lump  the  shape  of  around 
ball,  is  that  it  may  not  supply  the  heat  too  sudden- 
ly to  the  saw.  If  this  lump  was  made  flat,  it  would 
supply  the  heat  too  suddenly,  unless  it  was  used  at 
a  very  low  temperature ;  it  is  evident  it  would  not 
then  temper  more  than  one  or  two  of  the  saws  be- 
fore it  would  require  to  be  reheated.  The  object  of 
having  this  round  lump  welded  upon  a  piece  of 
round  bar,  is  for  the  convenience  of  keeping  the 


160         HARDENING   AND   TEMPERING   OF    STEEL. 

lump  in  position  upon  the  anvil,  and  to  prevent  the 
operator  from  always  being  in  a  stooping  position 
when  tempering  the  saws.  The  iron  being  finished, 
it  is  now  ready  to  be  heated  for  tempering  the  saws. 
The  large  lump  will  require  to  be  heated  to  a  red 
heat,  after  which  the  opposite  end  of  the  iron  must 
be  placed  in  the  hole  in  the  anvil.  The  saws  may 
now  be  placed  (one  at  a  time)  upon  the  lump ;  a 
slow  rotary  motion  must  be  given  to  the  saw,  by  the 
use  of  a  small  stick  of  wood,  in  order  to  equalize 
the  heat.  The  end  of  the  round  bar  at  the  top  of 
the  lump  will  help  to  supply  heat  and  keep  the  saw 
in  position  whilst  it  is  being  turned  round  upon  the 
lump.  As  soon  as  a  light  straw  color  appears  upon 
the  saw,  it  must  be  taken  off  the  iron  and  cooled, 
either  in  water  or  oil ;  or,  if  the  heat  has  not  been  too 
suddenly  applied,  the  saw  may  be  allowed  to  cool  in 
the  air  of  its  own  accord.  These  kinds  of  small  cir- 
cular saws  are  generally,  after  hardening,  convex  on 
one  side  and  concave  on  the  other.  This  imperfec- 
tion is  owing  to  the  outer  part  of  the  saw  becoming 
too  small  to  contain  the  central  part.  When  the 
practice  of  securing  the  saws  upon  the  spindle  by 
circular  plates  screwed  firmly  against  each  side  is 
adopted,  a  small  degree  of-  regular  convexity  is  not 
very  detrimental,  because  the  plates  bring  the  saw 
straight ;  but  when  they  are  convex  in  a  greater  de- 
gree, they  will  require  to  be  slightly  hammered. 
The  outer  part  of  the  saw  is  the  part  which  requires 
to  be  hammered,  in  order  to  expand  the  outer  part 
and  bring  the  middle  fiat. 

These  kinds  of  saws  may  be  tempered,  and  the 


HARDENING   AND   TEMPEEING    OF    STEEL.         161 

trouble  of  brightening  their  surfaces  spared,  by 
smearing  them  with  oil  or  tallow  and  holding  them 
one  at  a  time  over  a  slow  clear  fire  until  the  oil  or 
tallow  begins  to  smoke,  after  which  the  saw  must 
be  immersed  in  oil  and  partly  cooled ;  it  must  then 
be  held  over  the  fire  a  second  time,  until  the  oil 
again  begins  to  smoke.  If  the  saw  is  immersed  in 
the  oil  and  held  over  the  fire  a  third  time,  it  will 
ensure  a  more  regular  degree  of  temper.  Care 
must  be  taken  each  time  the  saw  is  heated  not  to 
raise  the  temperature  beyond  that  which  is  neces- 
sary to  cause  the  oil  to  smoke ;  otherwise  the  saw 
will  become  too  soft  for  the  purpose  it  is  intended 
for — namely,  cutting  hard  substances.  By  this 
method  the  saws  acquire  the  same  temper  as  that 
which  they  acquire  when  tempered  to  a  straw 
color.  A  large  quantity  of  these  kinds  of  saws 
may  be  tempered  more  expeditiously  by  threading 
them  upon  a  piece  of  iron  wire,  and  then  placing 
them  in  a  proper  vessel,  with  as  much  oil  or  tallow 
as  will  cover  them  (the  wire  is  for  convenience  in 
lifting  the  saws  out  of  the  vessel),  and  then  to  place 
the  whole  over  a  small  clear  fire,  or  over  a  gas 
flame,  until  the  oil  or  tallow  begins  to  smoke,  after 
which  the  saws  must  be  taken  out.  They  may  then 
be  cooled  in  water  or  oil,  or  they  may  be  allowed 
to  become  cool  in  the  air.  This  indicates  the  same 
temper  as  that  called  a  straw  color. 

Saw-blades  which  are  required  for  sawing  wood 
require  to  have  the  greatest  amount  of  elasticity 
given  to  them ;  consequently,  after  they  are  hard- 
ened, they  will  require  to  be  tempered  to  the  same 


162         HARDENING   AND   TEMPERING   OF   STEEL. 

temper  as  that  called  spring  temper.  This  may  be 
done  by  exposing  the  blade,  the  surface  of  which 
has  been  brightened,  to  the  regulated  heat  of  a 
plate  of  metal  till  the  surface  has  acquired  a  blue 
color ;  or  it  may  be  heated  in  a  sand-bath  heated  to 
the  proper  temperature.  To  spare  the  trouble  of 
brightening  them,  they  may,  like  small  circular 
saws,  be  smeared  with  oil  or  tallow  and  heated 
over  a  clear  fire.  It  is  obvious  that  the  softer  the 
steel  is  intended  to  be  the  more  grease  must  be 
burnt  off;  consequently  those  saw-blades  which 
are  required  for  sawing  wood,  and  which  require 
to  be  sharpened  with  the  file,  will  require  to  be 
heated  till  thick  vapors  are  emitted  and  burn  off 
with  a  blaze;  two  or  three  reheatings,  and  partly 
cooling  them  in  oil  when  tempering,  will,  of  course, 
insure  a  more  uniform  degree  of  temper.  Saw- 
blades  which  are  required  for  sawing  wood,  could, 
like  those  intended  for  sawing  metals,  be  heated 
and  tempered  in  hot  oil;  but,  perhaps,  it  would 
not  be  very  economical.  The  oil,  of  course,  would 
require  to  be  heated  to  a  very  high  degree,  in  order 
to  impart  to  the  saws  a  spring  temper ;  so  that  it  is 
questionable  whether  the  time  saved  by  this  method 
would  be  sufficient  to  compensate  for  the  waste  of 
oil,  which,  at  this  high  temperature,  is  considera- 
ble ;  consequently,  it  becomes  those  who  have  such 
things  to  temper  to  adopt  those  methods  which  will 
answer  their  purpose  the  best.  Saw-blades,  unless 
hardened  in  a  current  of  air,  are  generally,  after 
hardening,  buckled  and  twisted  in  various  direc- 
tions ;  this  is  caused  by  an  unequal  contraction  of 


HARDENING  AND  TEMPERING  OF  STEEL.    163 

the  blade,  and  it  would  be  almost,  if  not  quite,  im- 
possible to  prevent  this  unequal  contraction,  when 
it  may  arise  from  so  many  causes.  The  metal  itself 
may  be  unequal  in  its  texture.  It  may  have  been 
rolled  at  a  temperature  which  was  not  uniform 
throughout  the  mass,  or  the  blade  may  have  been 
hammered  more  in  one  part  than  another ;  this 
would  be  sufficient,  from  its  unequal  density,  to 
cause  unequal  contraction ;  or,  if  the  temperature 
is  not  uniform  throughout  the  blade  when  it  is  im- 
mersed in  the  hardening  fluid,  it  will  cause  unequal 
contraction. 

Saw-blades  which  have  become  buckled  and 
twisted  in  hardening,  will,  after  they  are  tempered, 
require  to  be  hammered  flat;  this  operation  re- 
quires a  considerable  amount  of  care  and  practice. 
It  is  obvious  that  the  blades  will  require  to  be  ham- 
mered at  every  part  except  those  which  are  buckled. 
The  hammering  draws  and  expands  those  parts 
which  are  not  buckled,  and  removes  the  unequal 
tension  which  has  been  caused  by  the  unequal  con- 
traction of  the  blade.  The  extent  to  which  the 
blade  will  require  to  be  hammered,  of  course,  can 
only  be  ascertained  by  experience. 

When  saw-blades  are  well  hammered,  and  the 
unequal  tension  has  been  removed,  they  are  then 
flat  and  more  uniformly  elastic ;  but  if  the  crust 
of  the  blade  be  partially  or  wholly  removed  by 
grinding,  or  in  any  other  manner,  the  elasticity  is 
proportionately  impaired,  and  to  restore  the  origi- 
nal excellence  of  this  property,  the  blade  will  re- 
quire to  be  again  hammered  and  afterward  blued. 


164:         HARDENING   AND   TEMPERING    OF    STEEL. 

Saws  require  to  be  made  of  the  best  cast  steel,  and, 
like  all  other  kinds  of  tools,  when  required  for  cut- 
ting brass,  require  very  sharp  cutting  edges ;  they 
require  also  to  be,  in  a  slight  degree,  harder  for 
brass  and  cast  iron  than  for  steel  or  wrought  iron, 
otherwise  they  soon  lose  their  sharp  edges. 

When  it  is  required  to  harden  a  single  saw,  such 
as  is  used  for  sawing  off  the  ends  of  wood  screws, 
or  for  sawing  off  the  ends  of  small  screw-bolts,  or 
for  occasionally  sawing  the  grooves  in  the  heads  of 
screws,  it  may  be  heated  to  a  cherry-red  heat,  and 
then  placed  flatways  and  horizontally  between  two 
lumps  of  tallow,  or  it  may  be  pressed  edgeways 
into  a  single  lump  of  tallow.  When  it  is  intended 
to  harden  the  saw  by  this  last  method,  the  saw 
should  be  slightly  hammered  at  the  back  previous 
to  heating  and  hardening  it,  otherwise  the  cutting 
edge  will,  in  hardening,  become  convex,  and  the 
back  edge  will  become  concave.  If  the  saw  be- 
comes crooked  sideways,  it  may  be  straightened  by 
slightly  hammering  it  with  the  pane  of  a  small 
hammer  at  the  concave  side,  at  the  same  time  press- 
ing with  the  fingers  upon  each  end  of  the  saw. 
The  saw  will  be  the  better  for  being  slightly  heated 
previous  to  hammering  it ;  it  may  be  heated  by 
placing  the  back  side  of  it  upon  a  piece  of  hot  iron. 
If  the  saw  should  be  found  too  hard  for  the  purpose 
it  is  intended  for,  the  back  edge  may  then  be  placed 
upon  the  hot  iron,  and  the  saw  tempered  to  a  light 
straw  color. 

When  it  is  required  to  harden  a  lathe  centre,  it 
may  be  heated  in  an  open  fire;  the  tapered  part 


HARDENING    AND    TEMPERING   OF    STEEL.          165 

only  requires  to  be  heated,  and  this  only  to  a  low 
red  heat ;  the  lowest  heat  that  it  will  harden  at  is 
the  most  advantageous,  as  the  centre  is  the  more 
likely  to  keep  true,  and  it. will  not  afterward  re- 
quire to  be  tempered.  It  must  be  immersed  end- 
ways and  perpendicularly  in  the  water.;  the  back 
end  of  the  centre  must  enter  the  water  foremost ; 
it  must  be  allowed  to  remain  in  the  water  until  it 
becomes  cool,  after  which  it  is  ready  for  use.  Lathe 
centres  for  large  lathes,  on  account  of  the  heavy 
weights  they  sometimes  have  to  carry,  ought  always 
to  be  made  of  the  most  tenacious  cast  steel,  which 
ought  only  to  require  a  low  red  heat  to  harden. 

When  it  is  required  to  harden  a  large  or  small 
quantity  of  fluted  or  other  kinds  of  rimers,  they 
may  be  heated  in  a  similar  manner  to  screw-taps, 
either  by  enclosing  them  in  an  iron  box,  and  sur- 
rounding them  on  all  sides  with  carbon,  and  placing 
the  whole  in  a  furnace  or  hollow  fire,  or  by  placing 
them  in  the  midst  of  the  ignited  fuel  of  a  small 
hollow  fire.  It  will  sometimes  be  more  advan- 
tageous to  heat  these  kinds  of  articles  in  red-hot 
lead,  especially  when  a  large  quantity  requires  to 
be  operated  upon,  because  this  is  a  very  expeditious 
method  for  heating  them,  and  they  generally  keep 
truer  in  heating  by  being  surrounded  on  all  sides 
with  the  uniform  temperature  of  the  lead,  conse- 
quently they  will  keep  truer  in  hardening.  The 
lead,  of  course,  must  be  heated  to  a  certain  tem- 
perature suitable  to  the  steel.  If  the  rimers  are 
made  of  the  best  cast  steel,  the  temperature  of  the 
lead  need  not  be  raised  higher  than  what  is  neces- 


166         HARDENING   AND   TEMPERING-  OF   STEEL. 

sary  to  heat  the  rimers  to  a  cherry-red  heat ;  if  the 
lead  is  too  hot,  it  will  burn  the  steel,  and  cause  the 
rimers  to  be  full  of  very  small  holes,  which,  of 
course,  will  unfit  them  for  the  purpose  for  which 
they  are  intended.  If  the  lead  by  chance  becomes 
too  hot,  it.  may  be  cooled  down  to  the  proper  tem- 
perature by  dipping  a  piece  of  cold  iron  into  it. 

When  it  is  intended  to  heat  small  rimers  in  red- 
hot  lead,  it  will  be  necessary  (previous  to  putting 
them  into  the  lead),  in  order  to  protect  them  from 
the  direct  action  of  the  heat,  and  to  prevent  the 
lead  sticking  to  them,  to  brush  them  over  with  a 
little  soft  soap,;  the  largest  and  middle-size  rimers 
will  be  the  better  for  being  brushed  over  with  black- 
lead,  mixed  with  water,  or  they  may  be  brushed 
over  with  a  mixture  of  lamp-black  and  linseed  oil. 
If  the  black-lead  and  water  is  used,  it  will  be  well 
to  dry  the  rimers  previous  to  putting  them  into  the 
lead,  otherwise  the  dampness  may  cause  the  lead  to 
fly  and  accidents  may  happen  from  it.  Whichever 
method  be  adopted  for  applying  the  heat  to  rimers, 
they  will  require  to  be  heated  to  a  cherry-red  heat, 
after  which  they  must  be  immersed  separately,  end- 
ways, perpendicularly  (except  half-round  rimers), 
and  slowly  in  the  water.  Half-round  rimers  are 
very  liable  to  become  crooked,  or  concave  on  their 
round  side,  owing  to  the  round  side  being  the  last 
to  become  cool ;  consequently,  they  will  require  to 
be  immersed  in  the  same  steady  manner  as  the 
other  kinds,  but  not  so  perpendicularly — they  will 
require  to  have  a  more  horizontal  inclination. 
They  may  be  immersed  perpendicularly,  provided 


HARDENING   AND   TEMPERING   OF    STEEL.         167 

they  are  slowly  moved  horizontally  in  the  water  in 
the  direction  of  the  round  side,  at  the  same  time 
that  they  are  being  immersed  endways,  It  must 
be  borne  in  mind  that  red-hot  lead  will  heat  the 
steel  much  quicker  than  the  ignited  fuel  of  the  fire ; 
consequently,  when  large  fluted  rimers  are  heated 
in  lead,  the  cutting  ribs  of  the  rimers  will  arrive  at 
the  proper  temperature  much  sooner  than  the  cen- 
tral parts  of  the  rimers,  or  before  the  innermost 
centre  becomes  at  all  heated ;  and  if  the  rimers 
are  immersed  in  the  water  the  moment  the  cutting 
ribs  become  sufficiently  heated  (and  they  may  be 
immersed  without  fear  of  breaking  them),  the  cen- 
tral parts  of  the  rimers  will  remain  soft;  conse- 
quently, if  large  fluted  rimers  become  crooked  in 
hardening,  they  may  be  easily  straightened.  They 
may  be  straightened  by  laying  them  upon  a  block 
of  hard  wood,  or  upon  a  block  of  lead,  and  then 
putting  a  piece  of  round  iron  (the  size  of  the  groove) 
into  the  groove  at  the  convex  side,  and  then  strik- 
ing the  iron  with  the  hammer.  If  the  rimers  be 
tempered  previous  to  striking  them  with  the  ham- 
mer, they  will  straighten  the  easier.  When  small 
fluted  rimers  are  heated  in  red-hot  lead,  they  be- 
come heated  through  almost  instantly  they  are  put 
into  the  lead ;  consequently,  it  must  be  obvious  that 
if  these  become  crooked  in  hardening  they  cannot 
be  straightened  in  the  same  manner  as  the  larger 
sizes  ;  therefore,  in  order  to  guard  against  their  be- 
coming crooked,  they  must  be  allowed  to  remain  in 
the  heated  lead  until  they  become  uniformly  heated 
to  their  innermost  centre,  and  then  immerse  them 


168        HARDENING   AND   TEMPERING   OF   STEEL. 

endways  and  perpendicularly  and  very  slowly  in  the 
water,  and  entirely  quench  them ;  and  if  any  of 
them  become  crooked,  it  will  be  well  to  soften  them 
again,  then  straighten  and  reharden  them.  Care 
must  of  course  be  taken  not  to  raise  the  temperature 
of  the  lead  higher  than  what  is  necessary  to  heat 
the  rimers  to  the  proper  temperature  suitable  for 
hardening  them.  The  method  I  have  myself  some- 
times adopted  when  hardening  fluted  rimers  is  this. 
I  have  heated  them  separately  in  red-hot  lead,  and 
then  immersed  them  separately,  endways  and  per- 
pendicularly, in  the  water,  having  the  water  of  a 
suitable  depth,  so  that  when  a  rimer  was  immersed 
and  the  extreme  end  of  it  made  to  touch  the  bottom 
of  the  tank  and  then  withdrawn,  it  would  harden 
the  cutting  edges  of  the  rimer  and  leave  sufficient 
heat  in  the  central  part,  so  that  the  rimer  would,  if 
it  were  crooked,  admit  of  being  straightened,  either 
by  placing  it  between  the  centres  of  a  turning  lathe, 
and  striking  it  upon  the  convex  side  with  a  sma^l 
wooden  mallet,  or  by  placing  it  upon  a  block  of 
hard  wood,  or  a  block  of  lead,  and  striking  upon 
the  convex  side  with  the  mallet.  As  this  method 
requires  a  great  amount  of  experience  and  dexterity, 
and  as  there  is  great  risk  of  the  rimers  breaking 
when  they  are  struck  with  the  mallet,  especially  if 
they  be  allowed  to  become  too  cool  previous  to  strik- 
ing, it  will  be  well,  perhaps,  for  the  operator  (in 
order  to  avoid  any  considerable  obstacle)  to  adopt 
the  method  previously  explained,  that  of  immersing 
them  endways,  perpendicularly,  and  slowly  in  the 
water,  and  entirely  quenching  them. 


HARDENING   AND   TEMPEKINO   OF   STEEL.         169 

Rimers  after  they  are  hardened  will  require  to 
be  tempered,  which  may  be  done  by  adopting  sim- 
ilar methods  to  those  to  be  adopted  for  tempering 
screw-taps.  Fluted  rimers  will  require  to  be  tem- 
pered to  a  yellowish- white,  or  light  straw  color ;  six 
and  eight  sided  rimers  will  also  require  to  be  tem- 
pered to  a  light  straw  color ;  square,  and  triangular, 
and  half-round  rimers  will  require  to  be  tempered 
to  a  dark  straw  color.  The  reason  why  square,  and 
triangular,  and  half-round  rimers  require  to  be  re- 
duced lower  in  temper  than  the  other  kinds  is,  that 
they  take  hold  of  the  work  so  deeply  that  they  are 
very  liable  to  break  by  the  force  requisite  to  turn 
them  round.  Six  and  eight-sided,  and  square  and 
half-round  rimers,  which  have  become  slightly 
crooked  in  hardening,  may  be  straightened  by 
screwing  a  chipping  hammer  (flat  face  uppermost) 
between  the  jaws  of  a  pair  of  vice ;  the  convex  side 
of  the  rimer  HI  ay  then  be  laid  upon  the  hammer 
face,  whilst  the  concave  side  is  slightly  hammered 
with  the  sharp  pane  of  a  small  hammer,  at  the  same 
time  pressing  with  the  fingers  upon  each  end  of  the 
rimer.  If  the  rimers  (previous  to  hammering)  be 
slightly  heated,  they  will  straighten  the  easier,  and 
be  less  liable  to  break. 

Small  drills,  gouge-bits,  centre-bits,  counter- 
sinks, gimblets,  bradawls,  or  sprig-bits,  etc.,  may 
be  expeditiously  hardened  by  dipping  their  cutting 
parts  into  red-hot  lead,  and  then  cooling  them  in 
water.  When  it  is  intended  to  dip  several  of  any 
of  these  kinds  of  articles  at  once  into  red-hot  lead, 
it  will  be  necessary  to  have  a  pair  of  tongs  with 
8 


170         HARDENING   AND   TEMPERING   OF    STEEL. 

long  jaws  for  gripping  the  articles.  One  of  the 
jaws  of  the  tongs  will  require  to  be  made  hollow 
inside,  and  the  other  jaw  made  flat ;  the  hollow 
jaw  is  for  convenience — for  binding  a  piece  of  wood 
into  it — so  that  if  the  articles  should  happen  to  be 
of  an  unequal  thickness  the  tongs  may  grip  them 
all,  as  the  most  prominent  parts  of  them  will  sink 
into  the  wood.  "When  the  wood  becomes  too  much 
worn,  it  may  be  replaced  with  another  piece.  Any 
quantity  of  these  articles  may  be  heated  as  expedi- 
tiously  as  a  single  article,  if  there  be  sufficient  lead. 
Gouge-bits,  gimblets,  bradawls,  or  sprig-bits,  will 
require  to  be  tempered  after  they  are  hardened. 
They  may  be  tempered  by  placing  them  upon  a 
piece  of  hot  iron  and  heating  them  until  a  blue 
color  appears  upon  their  surfaces,  and  then  pushing 
them  off  the  hot  iron  into  a  vessel  containing  cold 
oil ;  or,  if  the  heat  has  not  been  too  suddenly  applied, 
they  may  be  allowed  to  become  cool  in  the  air  of 
their  own  accord.  A  large  quantity  may  be  tem- 
pered at  once  by  placing  them  in  a  proper  vessel 
with  as  much  oil  or  tallow  as  will  cover  them,  and 
then  placing  the  whole  over  a  small  fire  and  slowly 
heat  the  oil  until  it  will  take  fire  if  a  light  be  pre- 
sented to  it,  but  not  so  hot  as  to  burn  when  the 
light  is  withdrawn.  The  articles  may  then  be 
lifted  out  of  the  oil  (that  is,  providing  the  vessel  is 
furnished  with  a  false  bottom),  or  the  whole  may 
be  tipped  out  of  the  vessel  upon  a  thin  sheet  of  iron 
which  is  slightly  curved  and  placed  in  a  slanting 
position,  with  a  vessel  placed  at  the  bottom  to  catch 
the  oil ;  the  articles  may  then  be  allowed  to  drain 


HARDENING  AND  TEMPERING   OF   STEEL.        171 

and  become  cool  of  their  own  accord,  they  will 
then  be  the  same  temper  as  if  their  surfaces  were 
blued  upon  hot  iron. 

Centre-bits  and  countersinks  for  cutting  wood 
require  to  be  tempered  to  a  purple  color.  The 
heat  may  be  applied  to  these  either  by  a  piece  of 
flat  bar  iron  or  by  an  iron  ring  heated  to  redness, 
or  they  may  be  placed  in  a  proper  vessel  contain- 
ing oil  or  tallow,  and  then  placed  over  a  small  fire 
and  the  whole  slowly  heated  until  the  oil  yields  a 
thick  black  smoke,  but  not  so  hot  as  to  take  fire 
if  a  light  be  presented  to  it.  The  articles  must  then 
be  taken  out  of  the  oil  and  allowed  to  become  cool ; 
they  will  then  be  the  same  temper  as  if  their  sur- 
faces were  changed  to  a  purple  color  upon  hot  iron. 

Red-hot  lead  is  an  excellent  thing  in  which  to 
heat  any  long  plate  of  steel  that  requires  hardening 
only  on  one  edge,  for  it  need  not  be  heated  in  any 
other  part  but  that  which  is  required  hard,  and  it 
will  then  keep  straight  in  hardening ;  at  least,  it 
will  keep  very  much  truer  than  if  it  were  heated 
in  the  midst  of  the  ignited  fuel  of  the  fire. 

If  a  long  steel  plate  which  requires  to  be  hard- 
ened only  on  one  edge,  be  heated  in  a  furnace  or  in 
the  midst  of  the  ignited  fuel  of  a  hollow  or  open 
fire,  and  then  the  whole  body  of  it  immersed  in  the 
water,  it  will  become  very  much  twisted  and  warped, 
and  will  cause  a  deal  of  trouble  to  set  it  straight 
again,  even  though  the  steel  be  tempered  previous 
to  being  hammered,  especially  to  those  who  are  un- 
acquainted with  the  way  of  hammering  and  setting 
steel  plates  in  a  hardened  state.  If  the  plate  be 


172    HARDENING  AND  TEMPERING  OF  STEEL. 

heated  throughout  its  body,  and  if  only  one  edge 
of  it  (the  edge  which  is  required  hard)  be  im- 
mersed in  the  water,  or,  in  other  words,  if  the  plate 
be  only  partially  immersed,  the  plate  will  become, 
in  a  great  degree,  concave  on  one  edge  and  convex 
on  the  other.  The  edge  of  the  plate  which  goes 
in  the  water  becomes  convex,  and  the  edge  which 
does  not  enter  the  water  becomes  concave.  This  is 
owing  to  that  part  of  the  plate  which  is  below  the 
surface  ol  the  water  contracting  and  becoming 
shorter  by  the  loss  of  heat,  and  compressing  the 
red-hot  part  of  the  plate  which  is  above  the  surface 
of  the  water  into  a  denser  state;  moreover,  after 
that  part  of  the  plate  which  was  below  the  surface 
of  the  water  has  become  quite  cool,  it  will  be  in  a 
slight  degree  longer  than  what  it  was  when  in  its 
soft  state,  consequently  this  has  a  tendency  to  push 
the  red-hot  part  of  the  plate  round,  and  thereby 
helping  to  cause  the  uppermost  edge  of  the  plate  to 
become  concave. 

After  the  whole  body  of  the  plate  has  become 
cool,  the  hardened  part,  as  well  as  the  soft  part  of 
the  plate,  will  sometimes  be  shorter  than  what  it 
was  previous  to  hardening,  even  though  the  hard- 
ened part  did  expand  longer  in  hardening.  This 
is  caused  by  the  soft  part  of  the  plate  contract- 
ing by  the  loss  of  heat  after  the  hardened  part  has 
become  cool,  and  thereby  compressing  the  hard- 
ened part  into  a  denser  state.  If  red-hot  lead  is 
used  as  a  source  of  heat,  and  the  edge  of  the  plate 
only  (which  is  required  hard)  be  put  into  the  lead, 
it  is  obvious  that  the  other  part  of  the  plate  will 


HARDENING   AND   TEMPERING-   OF    STEEL.         173 

remain  cool ;  consequently,  when  the  plate  is  en- 
tirely immersed  in  water,  the  hot  part  of  the  plate 
will  not  act  with  sufficient  force  to  alter  the  cool 
part,  consequently  the  cool  part  of  the  plate  tends 
to  keep  the  hardened  part  true.  It  may  be  inquired, 
if  the  part  which  goes  in  the  lead  expands  longer 
in  hardening,  and  is  not  able  to  act  with  sufficient 
force  to  compress  the  cool  part,  will  not  the  hard- 
ened part  become  twisted  and  buckled  ?  The  an- 
swer to  this  is :  it  will  not  become  twisted  or  buckled 
by  the  expansion  (though  it  may  become  crooked 
in  a  slight  degree  by  the  unequal  hammering,  or 
the  unequal  density  of  the  steel),  because  the  heated 
part  of  the  plate  has  been  compressed  by  the  cool 
part  during  the  time  it  was  expanded  by  the  heat, 
consequently  the  expansion  will  generally  be  about 
equal  to  the  compression,  and  the  plate  will  be 
about  the  same  dimensions  that  it  was  previous  to 
hardening. 

Should  the  hardened  part  of  the  plate  happen 
to  become  in  a  slight  degree  longer  than  what  it 
was  previous  to  hardening,  it  is  a  proof  that  the 
expansion  predominates  over  the  compression ;  if,  on 
the  contrary,  it  becomes  shorter,  it  is  a  proof  that 
the  compression  predominates  over  the  expansion. 

When  it  is  intended  to  heat  articles  in  red-hot 
lead,  they  ought  not  to  be  plunged  too  quickly  into 
the  lead  :  plunging  cold  steel  too  suddenly  into  red- 
hot  lead  has  a  tendency  to  cause  it  to  become 
crooked  in  a  similar  manner  as  red-hot  steel  be- 
comes crooked  when  it  is  plunged  too  suddenly  into 
cold  water. 


174:    HAEDENING  AND  TEMPERING  OF  STEEL. 

All  articles  which  are  heated  in  red-hot  lead 
should  be  slightly  moved  up  and  down  in  the  lead 
during  the  time  they  are  becoming  heated,  other- 
wise the  heat  will  be  apt  to  terminate  in  a  strict 
line,  and  will  probably  cause  them  to  crack  when 
they  are  immersed  in  the  water. 

A  very  good  vessel  in  which  to  heat  the  lead 
when  one  edge  of  a  long  plate  is  required  to  be 
heated,  is  made  by  taking  a  piece  of  three-inch 
angle  iron,  a  few  inches  longer  than  the  plate  to  be 
hardened,  and  slitting  and  turning,  and  welding 
each  end  of  the  angle  iron  so  as  to  form  a  kind  of 
trough.  A  long  fire  will  be  required  for  heating 
the  angle  iron  and  the  lead.  A  fire  of  any  length 
may  be  made  by  taking  a  piece  of  wrought  iron 
pipe,  and  boring  some  holes  into  it  in  the  direction 
of  its  length.  The  holes  will  require  to  be  about 
five-eighths  of  an  inch  in  diameter,  and  about  three 
inches  apart;  one  end  of  the  pipe  must  then  be 
inserted  into  the  aperture  of  the  tuyere.  A  row 
of  bricks  must  be  placed  on  each  side  of  the  pipe, 
at  a  suitable  distance  from  it,  so  as  to  leave  room 
for  the  fuel  and  the  angle  iron  between  the  bricks. 
The  pipe  will  require  to  be  covered  over  with  loam 
or  fire-clay,. in  order  to  keep  it  from  burning;  pre- 
vious to  covering  the  pipe  over,  each  hole  should 
be  stopped  with  a  piece  of  wood,  so  that  the  loam 
may  not  get  into  the  pipe,  or  stop  up  the  holes  in 
the  pipe ;  after  the  covering  up  of  the  pipe  is  com- 
pleted, the  pieces  of  wood  may  then  be  pulled  out 
of  the  holes,  and  the  fire  lighted.  The  fire  will 
burn  with  more  regularity  if  the  first  three  or  four 


HARDENING  AND  TEMPEKING  OF  STEEL.    1Y5 

holes  (at  that  end  of  the  pipe  which  enters  the 
tuyere)  be  a  little  larger  than  the  others,  as  the 
blast  is  always  strongest  at  the  far  end  of  the  pipe. 
A  loose  plug  will,  of  course,  be  required  for  the  far 
end  of  the  pipe  to  stop  the  blast;  and  if  at  any 
time  the  pipe  becomes  stopped  by  the  ashes  falling 
through  the  holes  of  the  pipe,  the  loose  plug  may 
be  taken  out,  and  the  ashes  blown  out  of  the  pipe ; 
the  plug  may  then  be  put  back  into  its  place.  If 
more  durable  things  than  the  angle-iron  and  pipe 
be  required,  a  long  fire-tile  may  be  chipped  out  to 
the  proper  shape,  and  made  to  answer  the  purpose, 
and  a  small  special  furnace  constructed  for  heating 
it.  A  pot  for  melting  a  small  quantity  of  lead  may 
be  made  by  welding  a  plug  into  one  end  of  a  piece 
of  wrought  iron  pipe  ;  but  this  is  not  very  durable, 
as  the  high  temperature  of  the  lead  will  soon  cause 
it  to  burn  into  holes,  and  allow  the  lead  to  run  out 
into  the  fire. 

When  a  more  durable  thing  than  the  wrought 
iron  pipe  is  required,-  and  a  larger  quantity  of  lead 
requires  heating,  a  crucible  similar  to  those  used  in 
brass  founderies  will  be  suitable;  Crucibles  contain- 
ing a  large  quantity  of  lead  cannot  conveniently  be 
heated  in  a  common  smith's  fire ;  consequently,  a 
suitable  furnace  must  be  constructed  for  the  pur- 
pose. When  it  is  necessary  to  heat  the  lead  in  a 
crucible,  it  should  be  made  red-hot  previous  to  put- 
ting the  lead  into  it ;  and,  in  heating  .the  crucible, 
the  same  plan  must  be  adopted  as  that  which  is 
generally  adopted  in  brass  founderies ;  namely,  put- 
ting the  crucible  in  the  fire  with  its  mouth  down- 


HARDENING   AND   TEMPERING   OF  STEEL. 

ward,  in  order  that  the  heat  may  act  upon  the  in- 
side and  the  outside  of  the  crucible  at  the  same 
time,  and  so  cause  a  more  uniform  expansion  of  the 
crucible,  and  lessen  the  risk  of  its  cracking.  The 
crucible  need  not  be  reversed  until  it  has  become 
red-hot ;  then  it  will  be  ready  to  receive  the  lead. 
If  the  crucible  be  put  in  the  tire  bottom  down- 
ward, the  heat  for  a  time  would  only  act  upon  the 
outside,  consequently  it  would  cause  an  unequal  ex- 
pansion, and  increase  the  risk  of  its  cracking. 

Another  thing  to  be  observed  is,  that  the  sur- 
face of  lead  when  melted  in  open  vessels  becomes 
quickly  covered  with  a  skin,  or  pellicle.  This  is 
occasioned  by  the  action  of  the  oxygen  of  the  at- 
mosphere, the  activity  of  which  soon  causes  the  skin 
to  increase  in  thickness,  and  wastes  the  lead  so  fast 
that  it  becomes  an  object  of  importance  to  those 
who  use  much  lead  to  check  its  formation,  or  con- 
vert it  when  formed  into  the  metallic  state  again. 
Charcoal,  or  fatty  substances,  assisted  by  sufficient 
heat,  convert  this  dross,  or  oxide,  into  metal  again ; 
.but  if  a  covering  of  charcoal  or  cinders  be  kept  on 
the  surface  of  the  melted  lead,  the  oxide  will  not 
form.  When  it  is  allowed  to  fbrm,  it  not  only 
wastes  the  lead,  but  is  a  great  obstruction  to  get- 
ting the  articles  in  and  out  of  the  lead. 

In  a  former  part  of  this  work  it  has  been  recom- 
mended to  allow  steel  when  heating  for  hardening 
(in  order  to  assist  the  process)  ample  time  to  soak 
and  become  uniformly  heated  to  its  innermost  centre. 
In  this  place  (on  the  subject  of  heating  steel  in  red- 
hot  lead)  it  is  stated  that  large  ffuted  rimers  may 


HARDENING  AND  TEMPERING  OF  STEEL.    177 

be  immersed  in  the  water  without  fear  of  breaking 
them  immediately  their  cutting  ribs  or  edges  become 
uniformly  heated  to  the  proper  temperature  suitable 
for  hardening  them,  without  waiting  for  the  central 
steel  to  become  heated.     As  this  will  probably  be 
noticed  by  some  persons  who  may  not  perhaps  give 
it  sufficient  thought  to  ascertain  the  true  meaning 
of  it,  it  will  tjien  appear  to  them  that  one  part  of 
the  work  is  in  contradiction  to  the  other  part ;  con- 
sequently, I  have  thought  it  necessary  in  this  place 
to  give  an  explanation  to  it  so  as  to  prevent  the 
reader  misunderstanding  it.     In  the  first  place,  it 
will  be  necessary  to  repeat  that  red-hot  lead  will 
heat  steel  much  quicker  than  the  ignited  fuel  of  the 
fire ;  consequently,  when  such  an  article  as  a  large 
fluted  rimer  is  dipped  into  the  red-hot  lead,  the  sur- 
face steel  will  become  uniformly  heated  before  the 
central  steel  has  acquired  sufficient  heat  to  cause  it 
to  expand  (at  least,  from  the  short  time  the  rimer  is 
in  the  lead  the  central  steel  can  only  become  expand- 
ed in  a  very  small  degree)  ;  consequently,  when  the 
rimer  is  immersed  in  the  water,  the  surface  steel  in 
cooling  has  not  to  compress  the  central  steel,  neither 
has  the  central  steel  to  contract  after  the  outer  crust 
is  fixed  ;  consequently,  a  large  fluted  rimer  may  be 
immersed  into  the  water  (without  risk  of  breaking 
it)  immediately  the  cutting  ribs  arrive  at  the  proper 
temperature  suitable  for  hardening  them.      If  the 
surface  steel  of  any  article,  when  placed  in  a  hollow 
or  open  fire,  could  be  uniformly  heated  without 
heating  or  expanding  the  central  steel,  there  would 
be  no  necessity  for  allowing  the  steel  to  soak  or  be- 
8* 


178        HARDENING   AND   TEMPERING   OF   STEEL. 

come  uniformly  heated  to  its  innermost  centre  :  but 
as  the  surface  steel  cannot,  in  a  hollow  or  open  fire, 
be  uniformly  heated  without  causing  the  central 
steel  to  become  heated  and  expanded  also,  it  be- 
comes then  quite  necessary  to  heat  the  central  steel 
to  the  same  temperature  as  the  surface  steel,  in 
order  that  the  central  steel  may  admit  of  being 
compressed  by  the  surface  steel  when  it  is  immersed 
in  the  water.  .When  the  central  steel  of  any  article 
becomes  heated  and  expanded,  and  not  sufficiently 
softened  to  admit  of  being  compressed  by  the  sur- 
face steel  (when  becoming  cool),  it  will  have  a  tend- 
ency to  hold  the  surface  steel  in  such  a  state  of 
tension  that  it  will  sometimes  cause  it  to  crack  in 
several  places,  and  the  surface  steel  will  sometimes 
shell  off  in  flakes ;  consequently,  it  must  be  seen 
that  if  the  central  steel  is  heated  at  all,  it  is  requisite 
to  heat  it  uniformly  with  the  surface  steel ;  it  will 
then  lessen  the  risk  of  its  breaking  in  hardening. 
For  further  information  upon  this  subject,  I  must 
refer  the  reader  to  the  chapter  upon  the  expansion 
and  contraction  of  steel. 

When  it  is  required  to  harden  large  or  small 
drifts  in  large  or  small  quantities,  they  may  be 
heated  in  a  similar  manner  as  screw-taps,  either  by 
enclosing  them  in  an  iron  box  and  surrounding 
them  on  all  sides  with  carbon,  and  placing  the 
whole  in  a  furnace  or  hollow  fire,  or  by  placing 
them  in  the  midst  of  the  ignited  fuel  of  a  hollow 
fire.  Whichever  method  be  adopted,  they  will  re- 
quire to  be  uniformly  heated  to  a  cherry-red  heat. 
When  they  arrive  at  the  proper  heat,  they  will  re- 


HARDENING-   AND   TEMPERING   OF   STEEL.         179 

quire  to  be  immersed  separately,  endways,  perpen- 
dicularly, and  slowly  in  the  water  ana  entirely 
quenched.  After  the  drifts  have  become  quite  cool 
and  been  taken  out  of  the  water,  they  will  require 
to  be  brightened  and  tempered ;  they  may  be  tem- 
pered by  adopting  similar  methods  to  those  which 
are  to  be  adopted  for  tempering  screw-taps.  Drifts 
will  require  to  be  tempered  to  a  brown  color. 

When  it  is  required  to  harden  a  quantity  of 
large  common  drills,  and  which  have  been  allowed 
to  become  quite  cool  after  having  been  forged,  they 
may  be  placed,  several  at  once,  or  as  many  as  con- 
venient, in  the  midst  of  the  ignited  fuel  of  a  very 
small  hollow  tire,  or  they  may  be  heated  in  an  open 
fire,  taking  care  to  keep  their  points  out  of  the 
hottest  part  of  the  fire  at  first,  and  gradually  draw- 
ing their  points  toward  the  hotter  part  of  the  fire 
as  the  upper  parts  become  heated.  A  considerable 
portion  of  the  drill  will  require  to  be  heated  to  a 
cherry-red  heat.  The  blast,  of  course,  must  be 
sparingly  used.  When  the  drills  arrive  at  the  prop- 
er heat,  they  must  be  taken  out  of  the  fire  sepa- 
rately. Those,  in  advance,  of  the  others  must  be  the 
first  to  be  taken  out ;  a  part  of  the  heated  portion 
of  the  drill  must  then  be  immersed  in  the  water. 
It  must  not  be  forgotten  that  it  is  requisite  to  put 
the  water  in  motion  previous  to  dipping  the  point 
of  the  drill  into  the  water,  or  otherwise,  to  give  the 
drill  a  vertical,  or  other  movement,  immediately  it 
arrives  to  the  proper  depth  in  the  water.  That  part 
of  the  drill  which  is  below  the  surface  of  the  water 
must  be  allowed  to  remain  in  until  it  becomes  quite 


180         HARDENING   AND   TEMPERING   OF   STEEL. 

cool,  after  which  it  must  be  taken  out,  and  the  cut- 
ting part  brightened,  which  may  be  done  by  rubbing 
the  surface  with  a  piece  of  grindstone,  or  with  an 
emery  stick,  or  with  a  piece  of  emery  cloth.  The 
drill  may  then  be  laid  upon  the  anvil,  or  any  other 
suitable  place,  whilst  another  is  drawn  out  of  the  fire 
and  treated  in  a  similar  manner.  The  heated  portion 
of  the  drills  which  were  not  immersed  in  the  water 
will  then  continue  to  supply  the  heat  to  temper  the 
cutting  parts  of  the  drills.  After  the  second  drill 
has  been  immersed,  it  may  be  placed  alongside 
the  first  drill,  and  another  drill  withdrawn  from  the 
fire,  and  so  on,  until  all  that  have  been  heated  have 
been  immersed.  The  hardener  must  of  course 
(during  the  time  he  is  drawing  the  drills  out  of  the 
fire  and  dipping  them  in  to  the  water)  have  his  atten- 
tion upon  those  he  has  placed  upon  the  anvil,  so  that 
he  may  see  when  the  cutting  parts  arrive  at  the  proper 
temper ;  as  soon  as  a  uniform  dark  straw  color  ap- 
pears upon  the  cutting  parts  of  the  drills,  they  must 
be  instantly  cooled  in  the  usual  manner,  otherwise 
the  upper  part  of  the  drills  may  continue  to  supply 
heat,  and  the  cutting  parts  will  become  too  soft 
Should  it  happen  that  the  heat  at  the  back  part  of 
any  of  the  drills  is  insufficient  to  temper  the  cutting 
part,  it  will  be  advisable,  in  order  to  complete  the 
tempering,  to  hold  the  drill  for  a  few  moments  in  a 
gas  flame,  if  the  gas  is  lighted ;  or  it  may  be  placed 
upon  a  piece  of  hot  iron,  if  there  is  a  piece  of  hot 
iron  ready  at  hand ;  or  a  few  hot  ashes  may  be 
drawn  out  of  the  centre  of  the  fire,  and  the  drill 
held  over  them.  All  drills  which  are  intended  to 


HARDENING  AND  TEMPERING  OF  STEEL.    181 

bore  holes  less  than  the  quarter  of  an  inch  (and 
when  a  quantity  are  required  to  be  hardened)  must 
not,  like  the  larger  kinds,  be  heated  and  partially 
immersed ;  but  their  cutting  parts  only  should  be 
heated  to  a  cherry-red  heat,  and  the  drills  wholly 
immersed  and  entirely  quenched.  They  may  subse- 
quently be  tempered  by  first  brightening  their  cut- 
ting parts,  and  then  placing  them  several  at  once 
upon  a  piece  of  bar  iron  heated  to  redness.  Their 
cutting  parts  must  be  allowed  to  project  some  dis- 
tance over  the  heated  iron,  otherwise  the  heat  will 
be  too  suddenly  applied.  As  soon  as  a  dark  straw 
color  appears  upon  their  cutting  parts,  they  must 
be  cooled  in  the  usual  manner. 

Miniature  drills,  such  as  those  used  by  clock- 
makers  and  others,  cannot  conveniently  be  heated 
in  the  midst  of  the  ignited  fuel  of  the  fire ;  though 
some  of  them  may  be  heated  in  charcoal  dust,  heated 
to  a  red  heat.  These  small  drills  are  generally 
heated  in  a  gas  flame,  or  in  the  flame  of  a  candle ; 
they  are  hardened  by  plunging  suddenly  their 
heated  points  into  a  lump  of  tallow  or  into  the  grease 
of  the  candle.  They  are  tempered,  if  found  too  hard, 
by  taking  a  little  of  the  tallow  upon  their  points, 
and  then  placing  them  in  the  flame  at  a  short  dis- 
tance above  the  point,  and  holding  them  there  un- 
til the  tallow  upon  the  point  begins  to  smoke  ;  the 
cutting  part  of  the  drill  is  then  of  the  same  temper 
as  if  it  were  brightened  and  tempered  to  a  straw 
color.  By  any  of  the  methods  just  explained,  the 
cutting  parts  of  drills  are  tempered  to  a  straw  color, 
while  the  rest  is  not  higher  than  blue,  so  that  the 


182    HARDENING  AND  TEMPEEING  OF  STEEL. 

] lability  of  their  breaking  when  in  use  is  greatly 
diminished. 

It  has  previously  been  stated  that  chipping- 
chisels  will  be  the  better  if  the  hammering  (when 
forging  them)  be  continued  until  the  cutting  part 
becomes  nearly  cool ;  and,  perhaps,  it  will  not  be 
amiss  to  state  here  that  it  is  better  to  harden  and 
temper  them  after  being  forged,  and  while  the  part 
above  the  cutting  edge  is  in  a  red-hot  state,  than  to 
allow  them  to  become  quite  cool,  and  then  to  re- 
heat them  for  hardening.  The  reason  for  this  is, 
greater  care  is  required  to  heat  them  properly  after 
they  have  become  quite  cool ;  consequently,  there 
is  greater  risk  of  the  effect  of  the  hammering  be- 
ing taken  off  again. 

When  a  large  quantity  of  chipping-chisels  have 
been  forged,  and  have  been  allowed  to  become  quite 
cool,  and  which  may  require  to  be  hardened  and 
tempered,  similar  methods  must  then  be  adopted, 
as  those  which  are  to  be  adopted  for  hardening  and 
tempering  the  largest  kinds  of  common  drills,  with 
the  exception  that  the  chisels  will  require  to  be 
tempered  to  a  violet  color,  that  is,  if  they  are  re- 
quired for  chipping  metals.  If  the  chisels  are  re- 
quired for  chipping  stone,  they  will  require  to  be 
tempered  to  a  purple  color.  The  force  required  for 
chipping  stone  being  less  than  for  metals,  it  is 
obvious  that  the  chisels  are  less  liable  to  break ; 
consequently  (in  order  to  prevent  them  wearing 
away  so  fast)  they  may  with  safety  be  left  in  a 
slight  degree  harder. 

When  it  is  required  to  harden  those  kinds  of 


HARDENING-  AND  TEMPERING  OF  STEEL.    183 

small  dripping-chisels,  which  are  used  for  chipping 
the  delicate  kinds  of  work,  they  must  not,  like  the 
larger  kinds,  be  heated  and  partly  immersed,  but 
their  cutting  part  only  should  be  heated  to  a  cherry- 
red  heat.  They  should  then  be  wholly  immersed 
and  entirely  quenched.  They  may  subsequently  be 
tempered  by  first  brightening  their  cutting  part, 
and  then  placing  them,  several  at  once,  upon  a 
piece  of  bar  iron  heated  to  redness.  As  soon  as 
their  cutting  part  becomes  changed  to  a  violet 
color,  they  must  be  instantly  cooled  in  the  usual 
manner. 

When  a  common  turning-tool  is  required  extra- 
ordinarily hard  for  cutting  very  hard  cast  iron,  it 
will  be  necessary,  in  the  first  place,  to  heat  the  tool 
to  a  red  heat,  and  then  give  it  a  judicious  hammer- 
ing until  it  becomes  nearly  cool,  after  which  it  will 
be  necessary  to  heat  some  lead  to  a  bright  red  heat ; 
a  small  quantity  of  charcoal  dust  must  be  placed 
upon  the  surface  of  the  heated  lead  to  prevent  oxi- 
dation. During  the  time  the  lead  is  becoming 
heated,  the  cutting  part  of  the  tool  should  be  heated 
to  a  low  red-heat  in  an  open  fire.  After  the  lead 
has  become  heated  to  a  bright  red  heat,  and  the 
cutting  part  of  the  tool  to  a  low  red  heat,  the  tool 
must  then  be  drawn  out  of  the  fire,  and  while  it  is 
at  a  red  heat  the  scale  must  be  removed  with  the 
file ;  the  cuttmg  part  of  the  tool  must  then,  as  soon 
after  filing  as  possible,  be  put  into  the  heated  lead. 
It  must  be  allowed  to  remain  in  the  lead  until  it 
becomes  heated  to  the  same  temperature  as  the  lead 
— a  bright  red  heat ;  after  which  it  must  be  taken 


184        HARDENING   AND   TEMPERING-   OF    STEEL. 

out  of  the  lead  and  instantly  plunged  into  a  bucket 
of  pure  cold  water,  and  a  rapid  movement  given  to 
it,  and  entirely  quenched ;  after  which,  when  taken 
but  of  the  water  and  ground  upon  the  grinding- 
stone,  it  is  ready  for  use.  By  this  method  the  steel 
acquires  a  greater  degree  of  hardness  than  will  be 
readily  imagined  by  those  who  have  never  tried  it. 

"When  it  is  required  to  harden  small  spiral 
springs  which  are  made  of  steel  wire,  or  springs 
for  locks,  or  any  of  the  other  kinds  of  slight  springs, 
they  will  require  to  be  uniformly  heated  to  a  cherry- 
red  heat,  and  then  immersed  in  cold  oil  (not  oil 
which  has  been  long  in  use  and  become  thick),  and 
entirely  quenched.  Springs  of  a  medium  thickness 
will  be  the  better  for  being  cooled  in  water,  the 
water  being  previously  heated  to  about  60  degrees 
of  heat,  and  the  surface  of  which  should  be  covered 
with  a  film  of  oil.  The  thickest  kinds  of  springs 
will  be  the  better  for  being  cooled  in  pure  water 
heated  to  about  70  degrees  of  heat.  Springs  require 
to  have  the  greatest  amount  of  elasticity  given  to 
them ;  consequently,  they  will,  after  they  are  hard- 
ened, require  to  be  tempered.  They  may  be  tem- 
pered separately  by  smearing  them  over  with  oil  or 
tallow  and  then  holding  them  over  a  clear  fire,  or 
in  a  hollow  fire,  or  in  the  inside  of  a  piece  of  large 
iron  pipe  inserted  in  the  midst  of  the  ignited  fuel 
of  an  open  fire,  and  uniformly  heating  them  until  a 
white  flame  burns  upon  them,  or,  in  other  words, 
until  the  grease  burns  off  with  a  blaze.  If  it  is  a 
spiral  spring  (or  any  other  kind  of  spring  which  is 
not  thicker  at  the  ends  than  at  the  central  part) 


HARDENING  AND  TEMPERING  OF  STEEL.    185 

which  is  being  tempered,  and  which  is  shorter  in  its 
length  than  the  length  of  the  fire,  it  will  be  very 
apt  to  become  heated  at  the  extreme  ends  first ;  con- 
sequently, as  soon  as  the  two  ends  arrive  at  the 
proper  temperature  (which  is  known  by  the  grease 
taking  fire)  the  spring  must  be  immersed  in  oil  :  it 
must  not  be  entirely  quenched,  but  must  be  taken 
out  of  the  oil  again  immediately,  and  then  again 
exposed  to  heat.  If  the  oil  upon  the  ends  takes  fire 
again  sooner  than  the  oil  upon  the  middle  part  of 
the  spring,  it  must  then  be  immersed  again  in  oil, 
and  then  again  exposed  to  heat,  and  so  on  until  the 
oil  burns  uniformly  upon  all  parts ;  otherwise  the 
spring  cannot  acquire  a  uniform  temper.  After 
the  spring  has  become  uniformly  heated  to  the 
proper  temperature,  and  the  oil  burns  uniformly 
upon  it,  it  must  then  be  again  immersed  in  oil,  then 
taken  out  again  immediately  and  allowed  to  become 
cool  in  the  air  of  its  own  accord.  It  will  then  be 
fit  for  use.  All  kinds  of  springs,  whatever  their 
shape  or  whatever  their  size,  may  be  tempered  per- 
fectly by  this  method.  It  must  be  borne  in  mind 
that  there  is  but  one  certain  temper  which  gives  to 
steel  its  greatest  amount  of  elasticity ;  consequently, 
the  stiffness  or  pliability  of  springs  must  be  regu- 
lated by  the  substance  and  shape  of  the  steel  from 
which  they  are  made.  A  very  convenient  way  of 
tempering  a  large  quantity  of  small  springs  at  once 
(they  must,  of  course,  be  previously  hardened),  and 
of  heating  them  uniformly,  no  matter  how  irregular 
their  shape,  provided  the  heat  is  not  too  suddenly 
applied,  is  to  bind  a  quantity  of  them  together  with 


186    HARDENING  AND  TEMPEBING  OF  STEEL. 

a  piece  of  iron  binding-wire  and  then  to  put  them 
into  a  suitable  vessel  with  as  much  oil  or  tallow  as 
will  cover  them.  Then  place  them  over  a  small 
clear  fire,  and  slowly  heat  the  whole.  Just  as  the 
oil  begins  to  boil  the  springs  must  be  lifted  out, 
when  a  white  flame  will  burn  uniformly  upon  the 
whole  of  them ;  they  must  then  be  immersed  into 
cold  oil, — they  need  not  be  entirely  quenched,  but 
they  may  be  taken  out  of  the  oil  again  immediate- 
ly and  allowed  to  become  cool  in  the  air  of  their 
own  accord,  and  when  cool,  they  will  be  like  those 
which  have  been  blazed  off  separately  over  the  fire, 
and  fit  for  use.  A  separate  spring  may  be  attached 
to  a  separate  piece  of  wire,  which  may  be  lifted  out 
of  the  oil  occasionally,  to  ascertain  when  the  whole 
is  at  a  proper  heat,  which  is  known  by  the  white 
color  of  the  flame  upon  the  spring. 

Large  springs  may  be  tempered  by  this  method, 
but  the  time  saved  with  large  springs  will  not  be 
sufficient  to  compensate  for  the  waste  of  oil ;  conse- 
quently, it  will  be  more  economical  to  temper  the 
largest  springs  by  blazing  over  the  fire. 

It  would  be  well  for  those  who  are  not  accus- 
tomed to  the  operation,  before  attempting  to  boil  a 
large  quantity  of  springs,  to  boil  a  single  one  in  a 
small  quantity  of  oil,  and  so  make  themselves  ac- 
quainted with  the  proper  temperature  of  the  oil, 
and  the  proper  temper  of  the  spring. 

I  will  now  bring  this  chapter  to  a  conclusion, 
not  because  I  have  no  more  to  say,  but  because  I 
do  not  think  it  necessary  to  say  more ;  but  I  may 
add,  that  the  hardness  of  cutting  tools  and  the  an- 


HARDENING   AND   TEMPEKIN&   OF   STEEL.          187 

gles  forming  their  edges,  must  be  varied  according 
to  the  strength  and  hardness  of  the  material  to  be 
worked.  The  harder  materials  require  tools  with 
more  obtuse-angled  edges,  and  no  cutting-tool  will 
act  upon  a  substance  harder  than  itself. 

The  number  of  turns  which  the  mandrel  of  the 
lathe  ought  to  make  in  a  given  time  must  also  be 
varied  according  to  the  strength  and  hardness  of 
the  material  to  be  worked.  The  velocity  of  rotation 
for  wood  can  scarcely  be  too  swift,  it  must  be 
rather  slow  for  lead,  brass,  copper,  gun-metal,  and 
bell-metal ;  still  slower  for  ordinary  cast  iron,  forged 
iron,  and  steel,  and  slowest  of  all  for  tempered  steel, 
and  chilled  cast  iron ;  or,  in  other  words,  for  cast 
iron  which  has  been  cast  in  iron  moulds,  or  other 
good  conductors  of  heat. 

The  reason  for  these  limits  is,  that  a  certain 
amount  of  time,  varying  with  the  material,  is  re- 
quisite for  the  act  of  cutting  to  take  place,  and  that 
the  tools,  if  much  heated,  will  instantly  become  soft 
and  cease  to  cut. 


CHAPTER  VII. 
EXPANSION  AND  CONTRACTION  OF  STEEL. 

A 

EXPANSION  and  contraction  belonging  to  this 
subject  is  the  enlargement,  or  increase,  or  decrease, 
in  the  bulk  of  the  steel,  as  the  case  may  be,  in  con- 
sequence of  a  change  in  the  particles  by  the  process 
of  hardening.  It  is  pretty  generally  known  to  those 
who  are  employed  at  the  process  of  hardening  steel, 
and  to  those  in  the  habit  of  fitting  up  various  kinds 
of  work  requiring  great  nicety,  that  the  hardening 
of  steel  often  increases  its  dimensions ;  so  that  such 
pieces  of  work,  fitted  with  nicety  in  their  soft  state, 
will  not  fit  when  hardened,  and  the  workman  has 
therefore  to  resort  to  the  process  of  grinding  or  lap- 
ping to  make  the  work  fit. 

The  amount  of  the  expansion  (or  the  amount  of 
the  contraction  of  steel)  cannot  be  exactly  stated,  as 
it  varies  according  to  the  size  of  the  steel  operated 
upon,  and  the  depth  to  which  the  steel  hardens ;  also 
in  the  different  kinds  according  to  the  amount  of  car- 
bon combined,  and  even  in  the  same  steel  operated 
upon  at  different  degrees  of  heat.  Steel  which  is  the 
most  liable  to  injury  by  excess  of  heat  is  the  most 
liable  to  these  expansions ;  and  steel  which  is  less  lia- 
ble to  injury  by  heat  is  the  most  liable  to  contrac- 
tions. As,  for  example,  the  more  carbon  the  steel 


EXPANSION   AND   CONTRACTION  OF   STEEL.        189 

contains,  the  greater  will  be  the  expansion  of  the 
steel ;  and  the  nearer  the  steel  approaches  to  the  state 
of  iron,  the  less  will  be  this  increase  of  bulk. 

Although  steel  expands  in  hardening,  it  is  not 
universal  for  pieces  of  all  sizes  to  increase  in  dimen- 
sions :  for  sometimes  it  is  smaller  in  dimensions  after 
hardening.  This,  at  first  sight,  appears  anomalous ; 
but  I  will  endeavor  to  give  an  explanation  of  it. 

Steel,  like  all  other  substances  composed  of  par- 
ticles, varies  in  its  dimensions  with  a  change  in 
temperature.  It  follows  that  when  the  steel  is  at  a 
red  heat,  the  natural  positions  of  its  particles  are  in 
a  measure  displaced,  and  it  is  expanded  to  a  great- 
er bulk  ;  and  when  immersed  in  water  and  suddenly 
cooled,  such  a  change  of  its  particles  takes  place  as 
to  make  it  hard  and  brittle.  It  also  contracts  to  a 
smaller  bulk  by  the  loss  of  heat ;  but  this  cannot  so 
rapidly  occur  at  the  central  part,  because  it  is  pro- 
tected by  the  surface  steel.  Consequently,  large 
pieces  of  steel  do  not  harden  all  through ;  or,  in 
other  words,  do  not  harden  properly  to  their  centres, 
but  toward  the  centre  the  parts  are  gradually  less 
hard,  and  will  sometimes  admit  of  being  readily 
filed  ;  and  as  it  is  only  the  outer  parts  of  the  steel 
which  harden  properly,  consequently  it  is  only  those 
parts  of  the  steel  which  harden  that  increase  in 
bulk.  When  the  steel  is  immersed  in  the  water,  the 
water  begins  first  of  all  to  act  upon  the  outer  crust 
of  the  steel,  and  then  cooling  it  gradually  toward 
the  centre.  The  outer  crust  being  the  first  to  part 
with  its  heat,  it  is  of  course  the  first  to  contract  and 
become  smaller.  The  outer  crust  in  contracting  is 


190        EXPANSION   AND   CONTRACTION   OF   STEEL. 

held  in  a  state  of  great  tension,  by  having  to  com- 
press the  central  steel  (the  central  steel  at  the  time 
being  expanded  by  the  heat).  While  the  surface 
steel  is  in  this  state  of  tension,  and  the  central  steel 
in  this  state  of  compression,  the  particles  of  the  sur- 
face steel  (by  the  strain)  are  displaced  at  a  greater 
distance  from  each  other,  and  the  particles  of  the 
central  steel  (by  the  compression)  are  compressed 
into  a  denser  state.  The  particles  of  the  central 
steel  being  compressed  into  a  denser  state,  it  causes 
the  central  steel,  after  it  has  become  quite  cool,  to 
occupy  less  space  than  what  it  did  previous  to  hard- 
ening. The  particles  of  the  surface  steel  become 
.hard  while  in  this  state  of  tension,  consequently  the 
hardened  part  of  the  steel  becomes  fixed,  and  can- 
not return  to  its  original  bulk :  consequently,  the 
hardened  part  of  the  steel  occupies  more  space  than 
what  it  did  previous  to  hardening. 

If  the  displacement  of  the  particles  of  tl^e  outer 
steel  predominates  over  the  compression  of  the  par- 
ticles of  the  central  steel,  the  piece  of  steel  under  op- 
eration will  then  be  larger  in  dimensions.  If  the 
compression  of  the  particles  of  the  central  steel  pre- 
dominates over  the  displacement  of  the  particles  of 
the  outer  steel,  the  piece  of  steel,  under  operation 
will  then  be  smaller  in  dimensions.  In  other  words, 
if  the  expansion  of  the  outer  steel  amounts  to  more 
than  the  compression  of  the  central  steel,  the  piece 
of  steel  will  increase  in  bulk ;  if  the  compression 
of  the  central  steel  amounts  to  more  than  the  expan- 
sion of  the  outer  steel,  the  piece  of  steel  will  then 
decrease  in  bulk.  The  expansion  of  the  steel  is 


EXPANSION   AND   CONTEACTION   OF   STEEL.        191 

greatest  when  it  is  heated  to  a  high  degree  of  heat 
before  immersion.  This  effect  is  owing  to  the  par- 
ticles being  displaced  at  a  still  greater  distance  from 
each  other,  and  which  may,  in  some  measure,  ac- 
count for  the  brittleness  of  steel  when  overheated. 
This  expansion  is,  in  some  measure,  reduced  in  tem- 
pering; and  this  effect  is  caused  by  the  hardness 
being  reduced  and  allowing  the  particles  to  partly 
rearrange  themselves  to  their  natural  positions. 

It  is  believed  by  some,  that  the  hardness  of  steel 
is  caused  by  the  compression  of  the  whole  of  the  par- 
ticles into  a  denser  state ;  in  confirmation  of  this, 
they  say  that  steel  after  hardening  always  looks  closer 
and  finer  in  the  grain.  Now,  if  this  were  the  only 
cause  of  steel  becoming  hard,  how  does  the  steel  get 
larger  in  dimensions?  Pieces  of  steel  of  all  sizes 
would,  according  to  this,  universally  become  smaller. 
The  compression  of  the  particles  of  the  central  steel 
into  a  denser  state  certainly  does  take  place,  as  I 
have  before  remarked ;  but  the  particles  of  the  out- 
er parts  of  the  steel  are  displaced  at  a  greater  dis- 
tance from  each  other,  or  the  steel  could  not  be- 
come larger  in  dimensions.  It  is  believed  by  some, 
that  if  a  piece  of  steel  (in  hardening)  increases  in 
bulk  in  one  part,  that  it  must  decrease  in  bulk 
in  proportion  in  another  part.  Now,  if  this  were 
the  case,  how  is  it  that  the  specific  gravity 
of  some  pieces  of  steel  is  reduced  by  hardening ; 
and  how  is  it  that  workmen  have  often  to  grind  or 
lap  pieces  of  steel  to  make  them  fit  the  same  places 
which  they  fitted  previous  to  hardening  3  It  may 
be  said  that  the  steel  may  be  prevented  from  fitting 


192        EXPANSION   AND   CONTRACTION   OF   STEEL. 

the  place  it  previously  fitted  by  becoming  crooked 
or  oval  in  hardening ;  but,  if  this  were  the  only 
cause,  how  could  it  be  made  to  fit  its  place  again  by 
grinding  or  lapping  ?  It  would  be  impossible  (un- 
less it  were  softened  and  upset)  to  make  the  lean  or 
concave  side  of  it  fit  its  place  again.  I  may  also 
inquire,  what  is  the  cause  of  steel  being  whiter  in 
color  after  hardening?  As  I  have  previously  re- 
marked that  it  is  only  those  parts  of  the  steel  which 
harden  properly  that  increase  in  bulk,  it  may  per- 
haps be  asked,  how  is  it  that  a  piece  of  bar  steel 
becomes  shorter  in  hardening  ?  The  answer  is,  that 
the  central  steel  is  compressed  by  the  surface  steel 
endways  as  well  as  sideways,  by  the  surface  steel 
contracting  shorter  by  the  loss  of  heat.  The  cen- 
tral steel  contracts  after  the  outer  crust  is  fixed,  con- 
sequently an  internal  strain  is  caused ;  and,  if  the 
steel  becomes  shorter  than  what  it  was  previous  to 
hardening,  it  is  because  the  force  of  this  internal 
strain  shortens  the  outer  steel  more  than  it  expands 
in  hardening. 

It  is  quite  reasonable  to  suppose,  if  the  particles 
of  the  hardened  parts  of  the  steel  are  removed  to  a 
greater  distance  from  each  other,  that  the  steel 
would  look  considerably  more  open  and  coarser  in 
the  grain ;  consequently,  it  may  be  inquired,  if  it  is 
not  the  compression  of  the  whole  of  the  particles 
into  a  denser  state,  what  is  the  cause  of  steel  look- 
ing closer  in  its  texture  after  hardening?  The 
answer  is,  if  we  accept  the  theory  that  it  is  the 
crystallization  of  the  carbon  which  causes  the  hard- 
ness in  steel,  that  the  carbon  expands  in  the  act  of 


EXPANSION   AND   CONTRACTION   OF   STEEL.        193 

crystallization  (in  a  similar  manner  that  water  ex- 
pands by  extreme  cold  in  crystallizing  into  ice)  and 
fills  up  every  pore  or  crevice,  and  gives  the  steel 
the  appearance  of  being  closer  and  more  solid. 

Such  is  a  slight  sketch  of  the  expansion  and  con- 
traction of  steel ;  and,  although  much  more  might  be 
said,  I  have  not  thought  it  necessary  to  entangle 
the  reader  with  a  lot  of  theories,  although  it  may  be 
necessary  for  his  amusement,  and  for  the  exercise 
of  sound  judgment,  to  occasionally  glance  at  them 
in  treating  fully  the  purely  mechanical  operations. 

The  expansion  of  steel  is  prevented  in  some 
measure  by  annealing  the  steel  about  three  times 
previous  to  its  being  finished,  turned,  or  planed ; 
for  instance,  after  the  first  skin  is  cut  from  the  steel 
it  should  be  annealed  again,  after  which  another 
cut  must  be  taken  from  it  and  again  annealed,  and 
so  the  third  time.  This  may  appear  to  some  like 
frittering  'away  time;  but  in  many  instances  the 
time  will  be  more  than  saved  in  lapping  or  grind- 
ing to  their  proper  sizes  after  the  articles  are  hard- 
ened, especially  when  it  becomes  necessary  to  lap  or 
grind  them  by  hand-labor,  for  hardened  steel  works 
with  great  difficulty ;  therefore  in  some  instances  it 
becomes  a  matter  of  importance  in  hardening  to  keep 
the  article  as  near  as  possible  to  its  original  size.  I 
have  myself  had  articles  to  harden  which  could  not 
be  lapped  or  ground  to  their  finished  dimensions  in 
the  turning-lathe  owing  to  their  peculiar  shapes,  so 
that  the  workman  has  been  compelled  to  adopt  the 
slow  process  of  lapping  with  a  copper  file  and  emery  ^ 
dust,  mixed  with  oil.  I  have  known  those  articles 
9 


194        EXPANSION   AND   CONTRACTION   OF   STEEL. 

which  were  only  once  annealed,  to  take  several  hours 
to  lap  them  to  the  finished  dimensions  after  they  were 
hardened ;  and  I  have  known  articles  of  the  same 
kind  and  of  precisely  the  same  dimensions  (in  their 
soft  state),  made  from  the  same  bar  of  steel  and 
heated  to  the  same  temperature  (as  near  as  the  eye 
could  judge),  and  hardened  in  water  of  the  same 
temperature,  which  have  been  annealed  three  times, 
scarcely  requiring  to  be  touched  with  the  copper  file 
after  they  were  hardened.  As  there  may  be  some 
persons  who  may  perhaps  require  an  article  to  be 
after  hardening  as  near  its  original  size  as  possible, 
and  who  may  not  perhaps  be  provided  with  such 
things  as  buffs,  laps,  or  stones,  I  presume  therefore 
that  this  hint  will  not  be  out  of  place  in  making 
those  acquainted  with  it.  Another  hint  deserves  a 
place.  I  have  found  that  articles  made  of  steel 
which  have  been  well  forged  will  always  keep  truer 
and  keep  their  original  sizes  better  in  hardening, 
and  be  less  liable  to  break  in  hardening,  than  arti- 
cles which  are  made  of  the  steel  in  the  state  it  leaves 
the  manufacturer ;  for  instance,  if  a  very  long  screw- 
tap,  or  long  rimer,  etc.,  be  required  for  any  special 
purpose,  it  will  be  well  to  take  a  piece  of  steel 
sufficiently  large  to  admit  of  being  forged  to  the 
required  dimensions.  If  for  a  long  screw-tap  or 
rimer,  three-quarters  of  an  inch  in  diameter,  seven- 
eighths  round-bar  steel  swaged  down  at  a  cherry-red 
heat  to  three-quarters  and  a  sixteenth  will  suffice 
(the  one-sixteenth  is  allowed  for  turning) ;  but  if 
the  edges  of  seven-eighths  square  steel  be  hammered 
down  so  as  to  form  eighth  squares  and  then  swaged 


EXPANSION  AND   CONTRACTION   OF   STEEL.       195 

down  to  three-quarters  and  a  sixteenth,  it  will 
prove  even  better  for  the  purpose  than  the  seven- 
eighths  round-bar  steel ;  it  must  be  obvious  that  if 
similar  methods  be  adopted  with  larger  articles, 
they  will  be  less  liable  to  break  in  hardening. 

To  make  mistakes  at  times  is  the  common  expe- 
rience of  all.  It  may  therefore  not  be  out  of  place 
to  say  a  few  words  upon  such  pieces  of  iron-work 
as  the  mechanic  may  have  the  misfortune,  through 
some  oversight  or  other,  to  bore  too  large,  and 
which  would  in  some  instances  cause  the  work  to 
be  useless  for  the  purpose  for  which  it  was  intended 
were  it  not  possible  to  contract  the  hole.  The  hole 
could,  in  some  instances,  be  set  in  by  heating  the 
work  at  the  forge,  and  then  hammering  it  upon  the 
anvil ;  but  if  the  shape  of  the  work  be  such  as  not 
to  admit  of  being  hammered,  or  if  there  be  not  suf- 
ficient metal  to  allow  hammering,  or  for  removing 
the  marks  caused  by  hammering,  it  will  be  obvious 
that  this  method  cannot  be  adopted.  Because  this 
method  cannot  be  adopted,  it  does  not  follow  that 
this  piece  of  work  should  be  condemmed  as  use- 
less ;  for  the  hole  may  be  contracted  by  adopting 
the  process  of  shrinking. 

It  must  not  be  understood,  according  to  the 
usual  term  shrinking,  that  the  work  should  be 
heated,  in  order  to  expand  the  metal  and  widen  the 
hole,  and  then  shrunk  upon  another  piece  of  work 
whose  diameter  is  larger  than  the  diameter  of  its 
own  hole :  for  by  this  method  it  must  be  obvious 
that  the  metal  cannot  return  to  its  original  bulk  ; 
consequently  the  hole  cannot  return  to  its  original 


196       EXPANSION   AND   CONTRACTION   OF   STEEL. 

diameter.  And  were  it  to  be  heated,  and  allowed  to 
become  cool  in  the  air  of  its  own  accord,  without 
being  shrunk  upon  another  piece  of  work,  it  could 
even  then  only  return  to  its  original  dimensions ; 
on  the  contrary,  the  piece  of  work  will  require  to 
be  uniformly  heated  to  a  red  heat,  and  then  im- 
mersed in  cold  water  and  entirely  quenched.  This 
method  causes  a  sudden  contraction  of  the  metal, 
consequently  the  hole  becomes  smaller.  If  this 
does  not  sufficiently  contract  the  hole,  the  operation 
must  be  repeated.  If  after  the  second  heating  and 
cooling  the  contraction  be  then  insufficient,  it  must 
be  operated  upon  a  third  time.  If  after  the  third 
heating  and  cooling  the  whole  be  not  then  sufficiently 
contracted,  it  will  be  next  to  useless  to  repeat  the 
operation,  as  the  particles  will  have  become  by  this  • 
time  in  their  most  condensed  state ;  at  least,  in  the 
most  condensed  state  they  are  capable  of  becoming 
by  this  operation  ;  and  instead  of  the  hole  contract- 
ing smaller,  it  will  become  oval,  likewise  wider  at 
each  end,  or,  as  the  term  is,  bell-mouthed.  If  it  is 
an  iron  or  steel  ring  or  collar  which  is  being  oper- 
ated upon,  it  will  be  found  that  even  in  the  first 
heating  and  cooling  it  will  cause  the  whole  to  be, 
in  a  slight  degree,  wider  at  each  end  than  at  the 
central  part.  This  is  owing  to  the  two  ends  or 
edges  of  the  ring  becoming  cool  sooner  than  the 
central  part  of  the  ring ;  and,  while  the  two  ends 
are  becoming  cool,  they  are  compressing  the  cen- 
tral part  into  a  denser  state.  The  central  part 
of  the  ring  contracting  after  the  two  ends  have 
become  quite  cool,  causes  this  unequal  contraction. 


EXPANSION   AND   CONTRACTION   OF   STEEL.        197 

This  unequal  contraction  might  in  a  measure  be 
prevented,  if  the  operator,  previous  to  heating  and 
cooling  the  ring,  take  the  trouble  of  shrinking  a 
narrow  collar  upon  the  outside,  at  each  end  of  the 
ring,  and  thus  cause  the  ring  to  cool  more  uniform- 
ly. Should  these  methods  not  have  the  desired 
effect  of  sufficiently  contracting  the  hole  (either  in 
an  iron  or  steel  ring),  there  is  another  source  open, 
simply  to  heat  the  ring  to  a  bright-red  heat,  and 
then  immerse  it  endways  and  perpendicular,  and 
half  its  depth  in  the  water,  leaving  the  other  half  to 
cool  in  the  air  above  the  surface  of  the  water.  As 
that  part  of  the  ring  which  is  below  the  surface  of 
the  water  becomes  cool,  it  compresses  and  thickens 
the  other  part  of  the  ring,  and  causes  the  hole  at 
this  compressed  end  of  the  ring  to  be  considerably 
smaller.  The  ring  will  require  to  be  reheated,  and 
again  immersed  in  a  similar  manner,  with  the  ex- 
ception that  the  ring  must  be  reversed ;  that  is,  the 
edge  which  was  uppermost  in  the  first  instance 
must  now  be  the  lower  edge.  This  method  will 
accomplish  what  the  other  methods  failed  to  do. 
This  operation  may,  if  found  necessary,  be  repeated 
several  times ;  but  there  is  a  limit  even  when  this 
method  is  adopted,  when  the  particles  will  assume 
their  most  condensed  state,  and  after  which  it  will 
be  useless  to  repeat  the  operation,  as  the  ring  will 
(even  though  it  be  made  of  iron)  ultimately  give 
way,  and  the  labor  will  be  lost.  King-gauges  which, 
have  become  worn,  may  generally  by  these  meth- 
ods be  contracted  sufficiently  to  allow  for  grinding 
them  to  their  original  sizes. 


CHAPTEE  Yin. 

CASE-HARDENING  OF  WROUGHT  IRON. 

IT  has  previously  been  shown  that  wrought  iron 
is  nearly  pure  decarbonized  iron,  and  not  possessed 
of  the  property  of  hardening.  But  I  will  now  en- 
deavor to  explain  a  process  by  which  articles  made 
of  wrought  iron  may  be  exteriorly  converted  into 
steel,  and  afterward  hardened.  The  process  is  called 
case-hardening,  and  is  an  operation  much  prac- 
tised, and  of  considerable  use;  and  in  this,  as  in 
most  of  the  other  arts,  differences  of  opinion  exist. 
Some  pretend  to  great  secrets  in  the  practice  of  this 
art,  using  many  fanciful  ingredients  to  which  they 
attribute  their  success ;  but  my  object  is  to  explain 
the  most  simple  and  common  method  adopted,  and 
that  which  I  have  found  in  my  own  experience  to 
produce  the  greatest  and  the  most  uniform  effect. 
Case-hardening  is  always  a  superficial  conversion 
of  iron  into  steel,  and  only  differs  from  cementation 
in  being  carried  on  for  a  shorter  time ;  for  it  is  sel- 
dom necessary  to  convert  the  iron  into  steel  more 
than  the  sixteenth  of  an  inch  deep,  unless  it  is  for 
certain  parts  of  machinery  where  great  stiffness  as 
well  as  hardness  is  required.  It  is  not  always  mere- 
ly foi  economy  that  iron  is  case-hardened,  but  for 
a  multitude  of  articles  for  various  purposes  it  is  bet- 


CASE-HARDENING   OF   WROUGHT   IRON.  199 

ter  than  steel :  for  it  lias  the  hardness  and  polish  of 
steel  externally,  with  a  core  of  soft  fibrous  iron  in 
the  centre :  for  example,  if  the  mandrels  of  lathes 
were  made  of  the  best  cast  steel  sufficiently  hard  to 
wear  well  in  the  collars,  they  would  be  liable  to 
break  by  the  twistings  and  sudden  checks  to  which 
they  are  at  times  subjected ;  but,  by  uniting  a  cer- 
tain quantity  of  steel  with  iron,  either  by  welding 
or  by  the  process  of  case-hardening,  the  danger  of 
their  breaking  is  avoided,  and  probably  serious 
accidents  avoided  also.  The  prussiate  of  potash 
renders  iron  nearly  as  hard  as  steel,  by  simply  heat- 
ing the  iron  to  a  red  heat,  and  sprinkling  the  pot- 
ash finely  powdered  upon  it,  and  then  plunging  the 
iron  into  pure  cold  water ;  but  the  hardness  by  this 
process  is  entirely  confined  to  the  surface,  and  for 
those  parts  of  machinery  which  have  to  endure  a 
large  amount  of  friction,  it  is  like  frittering  away 
time  to  case-harden  them  with  the  prussiate  of  pot- 
ash ;  but  for  some  kinds  of  articles  not  exposed  to 
much  wear,  a  sufficient  coating  of  steel  may  be  ob- 
tained by  this  process.  A  much  greater,  and  the 
most  uniform  effect  may  be  produced  by  a  perfectly 
tight  box,  and  animal  carbon  alone,  such  as  horns, 
hoofs,  or  leather,  just  sufficiently  burnt  to  admit 
of  being  reduced  to  powder  in  order  that  more 
of  it  may  be  got  into  the  Box  with  the  articles ; 
bones  reduced  to  dust  will  answer  the  purpose 
equally  as  well.  The  box  intended  for  the  purpose 
of  case-hardening  should  be  made  of  plate  iron; 
the  plate  iron  should  not  be  less  than  one-eighth 
part  of  an  inch  in  thickness ;  if  the  box  is  required 


200  CASE-IlARDENItfa   OF  WROUGHT   IRON. 

to  be  used  frequently,  the  plate  should  not  be  less 
than  three-eighths,  or  one-half  inch  in  thickness, 
otherwise  the  box  will  soon  be  worn  out.  The  size 
and  shape  of  the  box  must,  of  course,  differ  accord- 
ing to  the  size,  shape,  and  quantity  of  articles  re- 
quiring to  be  operated  upon.  As  the  iron  boxes 
must  vary  in  their  construction,  and  in  order  to 
make  this  subject  as  short  and  plain  as  possible,  let 
us  suppose  a  square  iron  box  to  be  already  made ; 
the  box  of  course  must  be  furnished  with  an  iron 
lid  (a  plain  piece  of  plate  iron,  the  size  and  shape 
of  the  interior  of  the  box),  two  holes  should  be 
pierced  in  the  lid  for  the  convenience  of  drawing 
testing  pieces  out  of  the  box  at  any  period  of  the 
process  if  required.  The  top  of  the  box  may  be 
strengthened  and  prevented  from  becoming  out 
of  shape  so  readily  by  the  heat,  by  taking  a  piece 
of  iron  about  three-quarters  of  an  inch  square, 
and  bending  and  welding  it  into  the  shape  of  the 
interior  of  the  box ;  and  after  boring  several  holes 
into  it,  it  must  then  be  riveted  to  the  box  at 
about  one  inch  distance  from  the  top ;  besides 
strengthening  the  box,  this  will  answer  for  the  iron 
lid  to  rest  upon,  and  thus  prevent  the  lid  from  press- 
ing upon  and  bending  the  articles  when  they  are  ex- 
panded by  the  heat.  By  placing  some  clay  or  loam 
between  this  iron  square  and  the  lid  it  makes  a  very 
secure  joint.  Two  holes  should  be  pierced  in  the  box 
at  opposite  sides,  just  above  the  lid,  for  the  conve- 
nience for  fastening  the  lid  in  its  proper  place  (with 
two  iron  pins),  and  making  tKe  joint  the  more 


CASE-HARDENING   OF   WROUGHT   IRON.  201 

For  occasional  case-hardening  upon  a  small 
scale,  a  very  good  box  may  be  made  by  welding  a 
plug  into  the  end  of  a  piece  of  wrought-iron  pipe, 
and  using  a  loose  plug  for  the  opposite  end ;  the 
loose  plug  will,  of  course,  require  to  be  fastened  into 
its  place  with  an  iron  pin  passing  through  it  and  the 
pipe ;  it  will,  of  course,  require  to  be  luted  with 
clay  or  loam  ;  part  of  the  plug  must  project  out  of 
the  pipe  for  the  convenience  of  pulling  it  out. 

It  may  happen  that  the  amateur  mechanic  may 
have  a  small  article  that  he  wishes  to  case-harden, 
and,  perhaps,  he  has  no  box  suitable  for  the  purpose, 
and,  perhaps,  he  has  no  convenience  for  making  one. 
In  such  an  instance  a  box  may  be  formed  of  loam  ; 
it  will  require  to  be  gradually  dried  before  it  is  ex- 
posed to  a  red  heat,  otherwise  it  will  probably 
crack. 

The  articles  intended  to  be  case-hardened  being 
previously  finished,with  the  exception  of  polishing, 
must  be  put  into  the  iron  box  in  alternate  layers  with 
the  animal  carbon,  commencing  on  the  bottom  of 
the  box  with  the  carbon  to  the  thickness  of  about 
three-quarters  of  an  inch ;  upon  this  a  layer  of  the 
articles  must  be  placed,  then  another  layer  of  carbon, 
about  one-third  part  in  thickness  of  the  first  will  be 
sufficient ;  upon  this  another  layer  of  the  articles 
and  carbon,  and  so  on  till  the  box  is  nearly  full,  fin- 
ishing with  a  layer  of  carbon,  about  the  thickness 
of  the  first  layer,  leaving  room  every  way  for  the 
expansion  of  the  articles  by  the  heat,  otherwise  they 
will  bend  each  other  in  the  box. 

After  the  packing  of  the  box  is  completed,  the 
9* 


202  CASE-HARDENING   OF   WROUGHT   IRON. 

lid  must  be  put  on  and  the  box  luted  with  clay  or 
loam,  in  order  to  confine  the  carbon  and  exclude  the 
atmospheric  air.  The  whole  must  now  be  placed  in 
a  suitable  furnace  or  hollow  fire.  The  fire  must  not 
be  urged,  as  the  contents  of  the  box  will  require  to  be 
very  gradually  and  uniformly  heated  to  a  red  heat ; 
the  whole  will  require  to  be  retained  at  this  heat  for 
a  period  answerable  to  the  depth  of  steel  required. 
In  half  an  hour  after  the  contents  of  the  box  have 
arrived  at  the  proper  uniform  temperature,  the  depth 
of  steel  will  scarcely  be  the  thickness  of  a  sixpence ; 
in  an  hour  about  double  the  depth,  and  so  on  till 
the  desired  depth  of  steel  is  acquired. 

It  may  be  asked  what  means  there  are  to  tell 
when  the  central  articles  arrive  at  the  proper  heat. 
The  answer  to  this  is,  a  practical  man  can  judge  by 
the  heat  of  the  fire  and  the  quantity  of  articles 
being  operated  upon ;  but  I  am  unwilling  to  refuse 
a  place  for  the  information  of  those  who  are  unac- 
customed to  the  operation,  therefore  I  have  sug- 
gested, in  order  to  prevent  the  operator  from  meet- 
ing with  any  considerable  obstacle,  that  two  holes 
be  pierced  in  the  lid  of  the  box  for  the  insertion  of 
testing  pieces,  so  that  at  any  period  of  the  process  a 
testing  piece  may  be  withdrawn  and  examined.  If, 
when  a  testing  piece  is  withdrawn,  it  be  not  suffi- 
ciently heated,  the  heating  must  be  continued  a 
little  longer ;  after  a  reasonable  time  another  piece 
may  be  withdrawn.  If  this  second  piece  is  suffi- 
ciently hot,  it  may  then  be  hardened  in  pure  cold 
water ;  it  can  then  be  broken  with  the  hammer, 
and  the  extent  of  the  carbonization  ascertained.  It 


CASE-HARDENING   OF    WROUGHT   IRON.  203 

must  Le  borne  in  mind  that  different  kinds  of  iron 
absorb  carbon  unequally ;  consequently,  the  testing 
pieces  will  require  to  be  made  of  the  same  kind  of 
iron  as  the  articles,  otherwise  they  will  afford  false 
results.  It  may  be  well  to  state,  that  the  more 
homogeneous  the  iron  the  more  equally  it  absorbs 
carbon ;  consequently,  the  less  likely  it  will  be  to 
alter  its  figure  in  hardening  than  iron  which  is  not 
homogeneous. 

To  save  breaking  or  using  any  of  the  articles  for 
testing  pieces,  plain  pieces  of  the  same  kind  of  iron 
as  the  articles  may  be  used  for  the  testing  pieces. 
The  testing  pieces  will  require  to  be  brightened; 
they  will  require  to  be  placed  (at  the  time  of  the 
packing  of  the  box)  in  the  central  part  of  the  box, 
and  placed  in  such  a  manner  that  they  may  be 
easily  pulled  out  of  the  box  through  the  holes  in 
the  lid,  either  by  a  piece  of  iron  wire  attached  to 
them,  or  the  pieces  may  be  made  long  enough  to 
project  through  the  holes  in  the  lid,  so  that  they 
may  be  gripped  with  the  pliers  and  withdrawn. 
The  holes  in  the  lid  must,  of  course,  be  luted  with 
loam  or  clay,  the  same  as  the  other  parts  of  the 
bgx. 

"When  the  articles  are  sufficiently  converted,  the 
box  must  be  drawn  from  the  fire,  the  lid  taken  off', 
and  the  contents  immersed  in  pure  cold  water,  and 
when  cold  and  taken  out,  they  are  ready  for  polish- 
ing. The  articles  may  (in  order  to  prevent  them 
from  rusting)  be  dried  by  riddling  them  in  a  sieve 
with  some  dry  sawdust,  after  which  they  may  be 
wiped  with  a  greasy  cloth. 


204:  CASE-HARDENING   OF   WROUGHT  IRON. 

If  the  articles  be  immersed  in  oil  instead  of 
water,  they  will  be  much  tougher  but  less  hard, 
though  sufficiently  hard  for  some  purposes.  It  is 
not  absolutely  necessary  to  immerse  the  articles 
either  in  water  or  oil,  direct  from  the  box,  as  it 
will  answer  equally  well  (and  sometimes  be  more 
convenient)  to  allow  them  to  remain  in  the  box 
until  they  become  cool,  and  then  reheat  them  in  an 
open  fire,  and  immerse  them  separately.  When 
the  case-hardening  is  required  to  terminate  at  any 
particular  part  of  an  article,  the  part  required  soft 
may  be  bound  with  thin  iron- wire,  and  then  cased 
with  loam.  This  will  prevent  the  carbon  coming  in 
contact  with  the  iron ;  consequently  it  will  prevent 
the  carbon  penetrating  the  iron,  or,  in  other  words, 
it  will  prevent  the  iron  from  absorbing  carbon  at 
the  part  where  the  wire  and  loam  is  placed.  The 
loam  will  require  to  be  gradually  dried  upon  the 
article,  previous  to  putting  it  into  the  box,  other- 
wise it  will  probably  crack. 

Another  method  is  to  shrink  an  iron  ring  or 
collar  very  tight  upon  the  part  not  requiring  to  be 
case-hardened  ;  but  this  mefhod  is  not  very  econom- 
ical, especially  when  a  large  quantity  of  articles 
requires  to  be  similarly  treated.  It  will  be  obvious 
that  to  make  and  fit  a  separate  collar  upon  each  of 
the  articles,  when  a  large  quantity  is  required  to  be 
operated  upon  at  once,  would  occupy  a  great 
amount  of  labor  and  time,  besides  a  great  amount 
of  time  will  have  to  be  expended  in  taking  the 
collars  off  again ;  and  as  time  is  money,  this  would 
become  a  very  expensive  method.  To  spare  the 


CASE-HARDENING   OF   WROUGHT   IRON.  205 

trouble  of  shrinking  a  collar  upon  the  article,  and 
to  prevent  the  operator  from  meeting  with  any  con- 
siderable difficulty  in  getting  the  collar  oif  again,  a 
collar  with  a  hole  somewhat  larger  in  diameter 
than  the  article  may  be  used;  the  space  between 
the  collar  and  the  article  must  be  filled  up  with 
loam.  There  is  more  economy  in  this  method  than 
in  the  method  of  shrinking  a  collar  upon  the  article, 
because  the  collar  can  be  easily  taken  off  and  put 
aside  to  be  used  again ;  whereas,  when  a  collar  is 
shrunk  tight  upon  the  article  it  has  generally  to  be 
cut  asunder  before  it  can  be  taken  off,  consequently 
the  collar  is  useless  for  future  use.  The  collar  may 
certainly  be  got  off  by  expanding  it  by  hammering  ; 
but  then  this  will  have  the  tendency  to  damage  the 
article,  that  is,  if  it  has  been  previously  finished  with 
the  exception  of  polishing.  If  the  article,  after 
being  cemented  with  the  carbon,  be  immersed  in 
the  water  previous  to  taking  the  collar  off,  the 
collar  will  become  hard,  because  it  has  absorbed 
carbon ;  consequently,  it  will  require  to  be  ground 
upon  the  grin  ding-stone  before  it  can  be  cut  off 
from  the  article,  either  by  the  chisel,  or  the  file,  or 
the  turning  tool. 

In  some  instances,  when  the  case-hardening  is 
required  to  terminate  at  any  particular  part,  it  will 
be  more  convenient  and  more  economical  to  post- 
pone the  finishing  of  the  article  until  after  it  has 
been  cemented  with  the  carbon. 

In  order  that  a  few  words  may  be  said  upon 
this,  we  will  for  example  take  the  mandrel  of  a 
turning-lathe.  Let  us  suppose  then  that  a  new 


206  CASE-HARDENING   OF    WROUGHT    IRON. 

case-hardened  mandrel  is  required  to  be  made. 
The  iron  selected  will  require  to  be  forged  by  the 
smith  to  the  proper  dimensions,  after  which,  when 
cold,  it  will  require  to  be  turned  in  the  turning- 
lathe  ;  those  parts  of  the  mandrel  which  will  require 
to  be  case-hardened  must  be  finished  (with  the  ex- 
ception of  grinding  and  polishing)  to  the  proper  di- 
mensions ;  those  parts  of  the  mandrel  not  requiring 
to  be  case-hardened  must  not  be  finished,  in  fact, 
it  is  immaterial  whether  they  be  turned  or  not, 
until  after  it  has  been  cemented  with  the  carbon. 
If  these  parts  of  the  mandrel  are  turned  previous  to 
cementing  it  with  carbon,  they  must  not  be  turned 
to  the  finished  dimensions ;  but  a  greater  amount 
of  metal  must  be  left  upon  these  parts  than  what  is 
required  when  it  is  in  a  finished  state. 

The  mandrel  being  ready  for  case-hardening,  it 
must  now  be  put  into  an  iron  box  with  as  much  ani- 
mal carbon  as  will  completely  envelop  it.  The  box, 
of  course,  will  require  to  be  luted  with  clay  or  loam, 
the  whole  must  now  be  placed  in  a  suitable  furnace 
or  hollow  fire  and  heated  in  a  similar  manner  as 
other  kinds  of  articles  when  requiring  to  be  case-hard- 
ened. When  the  mandrel  is  sufficiently  converted, 
the  box  must  be  drawn  out  of  the  fire  ;  the  mandrel 
must  be  allowed  to  remain  in  the  box  until  it  be- 
comes quite  cool,  after  which  it  is  ready  for  the  turn- 
ing-lathe. The  case-hardening  can  now  be  made  to 
terminate  at  any  particular  part  of  it,  by  turning 
the  superfluous  carbonized  metal  off,  after  which  it 
may  be  reheated  in  an  open  fire  and  hardened  in 
pure  cold  water.  The  carbon  once  added,  the  hard- 


CASE-HARDENING   OF    WROUGHT   IRON.  207 

ness  and  softness  may  be  reversed  backward  and 
forward  much  in  the  same  manner  as  steel. 

Iron  cemented  with  animal  charcoal,  however 
skilfully  the  operation  is  performed,  is  never  as  te- 
nacious as  iron  cemented  with  wood  charcoal ;  con- 
sequently, it  is  unfit  for  cutting-tools,  as  it  will  not 
take  a  fine,  firm  edge,  and,  were  it  to  pass  through 
the  process  of  forging  and  melting,  it  is  question- 
able, even  then,  whether  it  is  in  the  nature  of  the 
material  to  produce  such  an  effect.  But  if  case- 
hardened  iron  has  never  been  tried  for  certain  kinds 
of  springs,  it  would  be  worthy  of  a  trial. 


OHAPTEE  IX. 

TOUGHENING  OF  STEEL  IN  OIL. 

HARDENING  and  tempering  of  steel  in  oil  is 
pretty  generally  known  to  be  no  new  process,  but 
the  toughening  of  large  masses  of  cast  steel  in  oil  is, 
however,  a  new  process  for  guns  ;  and  in  the  present 
system  of  manufacturing  built-up  guns,  it  is  more  than 
probable  that  it  becomes^necessary  to  make  certain 
parts  of  them  of  steel  (toughened  in  oil.)  And  here 
I  must  in  justice  to  that  gentleman  mention,  that 
Mr.  Anderson  was  the  first,  so  far  as  I  know,  who 
ever  attempted  to  operate  upon  large  masses  of  cast 
steel,  such  as  are  now  operated  upon  for  guns.  The 
successful  results  in  this  case,  and  the  toughness  ac- 
quired in  the  material  by  the  process,  deserve  to  be 
noted,  as  it  is  not  generally  known,  and  the  infor- 
mation may  occasionally  prove  useful  to  the  engi- 
neer. I  may  state  that  the  rapid  extension  of  rail- 
roads has  led  to  numerous  improvements  in  the 
material  for  rails ;  and,*  as  they  require  to  be  of  the 
safest  and  most  durable  metal,  it  is  quite  probable 
that  rails  made  from  ingots  of  mild  cast  steel  will 
in  time  supersede  all  other  cheaper  but  less  durable 
materials.  It  will  be  readily  imagined  that,  the 
more  homogeneous  the  metal,  the  better  it  will  be 
for  the  purpose  of  railway  bars.  Cast  steel,  from 


TOUGHENING    OF    STEEL   IN   OIL.  209 

having  been  in  a  state  of  fusion,  is  more  homoge- 
neous than  the  usual  metal ;  and,  when  it  is  free  from 
all  other  substances,  except  a  very  small  portion  of 
carbon  (which  is  necessary  to  form  mild  steel),  its 
qualities  then  render  it  eminently  well  adapted  for 
railway  bars ;  and  I  am  myself  inclined  to  think 
that,  as  soon  as  it  can  be  cheapened  (and  I  have  my 
reasons  for  believing  that  it  can  be  cheapened),  it 
will  be  universally  adopted,  while  wrought  and  cast 
iron  for  the  purpose  will  become  things  of  the 
past. 

Railway  bars  require  to  be  not  only  homogeneous 
in  metal  but  in  the  temper  also ;  but  it  must  not  be 
understood,  according  to  the  usual  term  temper 
among  mechanics,  that  the  bars  should  undergo  the 
regular  process  of  hardening,  and  then  be  reduced 
to  a  blue,  or  any  other  color ;  on  the  contrary,  it  is 
quite  reasonable  to  suppose,  from  the  small  amount 
of  carbon  which  steel  suitable  for  railway  bars  con- 
tains, that  tbe  bars  can  be  submitted  to  no  process 
of  preparation  so  suitable  as  that  of  heating  them 
uniformly  in  a  suitable  furnace  to  a  bright  red  heat, 
and  then  entirely  quenching  them  in  oil,  which  will 
leave  them  in  the  toughest  and  most  uniform  state 
that  mild  steel  is  capable  of  receiving.  I  can  speak 
from  experience  that  a  bar  after  undergoing  this 
operation  will  admit  of  a  very  great  change  of  form 
without  diminution  of  its  cohesive  power ;  and  it  is 
quite  probable,  from  the  greater  hardness  of  the 
steel,  that  the  bars  will  be  less  liable  to  waste  by 
the  action  of  the  wheels.  The  bars  being  uniform 
in  temper  throughout,  it  is  obvious,  when  the  upper 


210  TOUGHENING  OF   STEEL   IN   OIL. 

surface  is  worn  away  by  the  friction  of  the  wheels, 
that  the  decay  will  not  be  more  rapid.  The  bars 
being  more  elastic,  they  will  be  less  liable  to  be 
broken  by  continual  jars  and  blows,  and  they  will 
probably  be  less  liable  to  rust  by  the  action  of  the 
atmosphere.  It  is  quite  probable,  also,  that  a  less 
weight  of  metal  might  be  used ;  but,  owing  to  so 
many  lives  and  the  vast  amount  of  property  which 
depend  upon  the  bars,  I  am  unwilling  to  recommend 
a  less  weight  of  metal.  For  many  other  purposes, 
however,  for  which  steel  is  used,  I  would  not  hesi- 
tate to  recommend  a  less  weight  of  metal  when  the 
steel  is  toughened  in  oil.  I  may  state  that  no 
danger  need  be  apprehended  of  the  steel  bars  be- 
coming cracked  by  this  process  (providing  they  be 
uniformly  heated  throughout).  Any  defect,  how- 
ever, whether  cracks  or  flaws,  which  could  not  be 
detected  while  the  bars  were  in  their  unequal  state 
of  temper,  will  by  this  process  be  made  visible.  I 
am  inclined  to  think  if  the  plates  belonging  to  the 
rollers  of  rag  engines  were  made  of  mild  cast  steel, 
and  toughened  in  oil,  that  they  would  be  more 
suitable  than  those  now  in  use. 

Should  there  be  some  who  are  more  attentive  to 
authority  than  reason,  and  who  inquire  by  whom  a 
process  is  used  rather  than  what  are  its  merits.  I 
assure  them  that  the  process  of  toughening  large 
masses  of  cast  steel  is  daily  practised  in  the  Gun 
Factories'  department  of  Her  Majesty's  Royal  Ar- 
senal, "Woolwich.  In  this  department,  with  a  very 
ingeniously  contrived  apparatus,  the  process  of 
toughening  large  masses  of  cast  steel  is  performed 


TOUGHENING   OF   STEEL   IN   OIL.  211   * 

in  the  following  manner: — A  block,  or  tube,  of 
mild  cast  steel  (or  steel  containing  a  smaller  propor- 
tion of  carbon  than  ordinary  cast  steel)  is  lifted  by 
a  powerful  crane  and  placed  in  a  perpendicular  po- 
sition in  an  upright  furnace ;  an  iron  coil  about  six 
inches  in  depth  and  about  one  inch  larger  in  di- 
ameter than  the  diameter  of  the  block  of  steel,  is 
placed  upon  the  fire  bars,  at  the  bottom  of  the  fur- 
nace, for  the  block  of  steel  to  rest  upon ;  beneath 
this  iron  coil  is  placed  a  piece  of  plate-iron  to  pre- 
vent the  cold  air  as  it  passes  through  the  bars  com- 
ing in  contact  with  the  extreme  end  of  the  block 
of  steel,  and  in  order  to  obtain  an  uniform  tempera- 
ture at  the  extreme  end  of  the  block  of  steel  this  iron 
coil  is  filled  with  wood  ashes.  The  iron  coil  becomes 
filled  with  the  wood  ashes  while  heating  the  furnace 
to  a  red  heat  with  refuse  wood  previous  to  putting 
the  steel  in  the  furnace.  After  the  block  of  steel 
is  placed  in  the  furnace,  the  bottom  end  of  it  is  then 
surrounded  with  some  short  blocks  of  wood;  the 
damper  is  not  lifted  until  the  extreme  end  has  ac- 
quired a  low  red  heat,  after  which  the  damper  is 
lifted,  and  the  block  of  steel  is  then  entirely  sur- 
rounded with  longer  pieces  of  refuse  wood,  thrown 
in  from  the  top  of  the  furnace.  The  steel  is  then 
slowly  heated  to  a  bright  red  heat  by  the  combus- 
tion of  the  fuel.  Wood  is  -used  as  fuel  on  account 
of  its  purity,  in  preference  to  coal  or  coke ;  it  is  not 
so  liable  to  degrade  the  steel,  but  has  a  tendency 
to  give  the  steel  pliability  without  diminishing  its 
hardness.  Just  as  the  steel  arrives  at  a  bright  red 
heat  the  vent  is  closed  for  a  few  minutes,  in  order 


212  TOUGHENING   OF    STEEL    IN   OIL. 

to  give  the  steel  ample  time  to  soak  and  so  r'eceive 
an  uniform  temperature  throughout  the  body  of  the 
steel.  For  the  more  uniform  the  temperature  the 
straighter  the  block  will  keep,  and  the  steel  will  ac- 
quire a  more  uniform  temper.  I  may  here  state  that 
the  heat  the  exterior  steel  receives  is  judged  of  by 
the  eye,  but  the  knowledge  of  the  heat  of  the  inte- 
rior steel  is  only  acquired  by  study,  by  attention, 
and  practice. 

After  the  steel  has  acquired  the  proper  uniform 
temperature  throughout,  the  travelling  crane  is  then 
brought  over  the  furnace,  the  cover  belonging  to 
the  top  of  the  furnace  is  then  removed,  after  which 
a  pair  of  large  iron  tongs  attached  to  the  crane 
fasten  themselves  at  the  top  end  of  the  steel  block 
or  tube.  The  tongs  are  so  constructed  that  the 
heavier  the  weight  the  tighter  they  grip  the  steel; 
still  it  is  found  necessary  to  turn  a  small  collar 
upon  the  end  of  the  block  to  prevent  the  tongs  slip- 
ping by  the  weight.  After  the  to'ngs  have  fastened 
themselves  upon  the  block  of  steel,  it  is  then  drawn 
out  of  the  furnace  and  sunk  into  a  large  iron  tank 
about  twenty  feet  deep,  containing  several  hundred 
gallons  of  oil.  The  heated  steel  in  passing  into  the 
oil  will  sometimes  cause  the  surface  oil  to  take  fire, 
which,  after  the  whole  body  of  the  steel  is  beneath 
the  surface  of  the  oil,  is  then  extinguished  by  clos- 
ing the  covers  at  the  top  of  the  tank  and  subse- 
quently covering  the  covers  with  a  piece  of  canvas. 
The  tank  has  a  water  space  which  surrounds  the 
oil — the  use  of  the  water  being  to  cool  the  oil. 
The  best  way  to  describe  the  tank  is  to  state  that 


TOUGHENING   OF    STEEL    IN   OIL.  213 

it  is  an  old  steam-boiler  sunk  endways  and  perpen- 
dicular in  the  ground. 

The  steel  in  parting  with  its  heat  raises  the  tem- 
perature of  the  oil,  and,  consequently,  raises  the 
temperature  of  the  water.  The  water  as  it  becomes 
heated  is  drawn  off  at  the  top  by  an  escape  pipe, 
and  a  supply  of  cold  water  is  continually  running  in 
at  the  bottom.  This  gentle  stream  of  water  run- 
ning through  the  tank  causes  the  heat  to  be  gradu- 
ally taken  from  the  mass,  and  the  whole  cools  uni- 
formly in  about  twelve  hours,  and  exceeding  tough- 
ness is  the  result  of  the  operation ;  while  it  is  thus 
made  much  higher  in  tensile  strength,  offering  a 
much  greater  resistance  to  compression.  It  is  also 
harder  and  more  elastic,  and  requires  a  much  greater 
force  to  break  it  with  the  hammer  ;  and  it  is  not  worn 
or  indented  so  readily  as  when  received  from  the  tilt, 
or  annealed.  This  operation  has  in  many  respects 
the  character  of  annealing,  yet  it  is  something  more ; 
for  it  is  quite  certain  that  a  different  change  of  the 
particles  takes  place,  as  it  leaves  the  steel  in  an  inter, 
mediate  state  between  hard  and  soft ;  and  when  mild 
cast  steel  is  required  in  this  particular  state,  it  can 
only  be  accomplished  by  a  slow  process  of  cooling  in 
oil,  or  some  other  liquid  of  the  conducting  quality 
and  which  requires  as  high  a  temperature  to  convert 
it  into  vapor.  Steel  containing  much  carbon,  oil  will 
harden  the  surface  very  much  more  than  its  internal 
parts,  so  that  it  will  resist  the  file ;  but  beneath  the 
surface  it  will  be  quite  soft.  In  steel  containing  a 
less  proportion  of  carbon  there  appears  to  be  very 
little  difference  between  its  external  and  its  internal 


214:  TOUGHENING   OP   STEEL   IN   OIL. 

parts.  In  theory  there  cannot  be  much  difference 
between  the  external  and  the  internal  parts  of  steel 
containing  such  a  small  amount  of  carbon,  and  not 
possessed  of  hardening  properties,  or  only  in  a  slight 
degree ;  and  in  practice,  the  theory  is  proved  to  be 
correct. 

I  may  here  state  that  the  solidity  and  strength 
of  all  substances  is  supposed  to  depend  upon  the 
strength  of  the  attraction  of  cohesion  between  their 
particles ;  because  the  stronger  this  is,  the  more  it 
opposes  the  disunity  of  the  body ;  consequently,  the 
attraction  of  cohesion  between  the  particles,  after 
the  steel  has  passed  through  this  process,  must  be 
stronger,  on  account  of  its  offering  a  greater  resist- 
ance to  separation.  It  must  not  be  imagined  that 
the  oil  penetrates  into  the  pores  of  the  steel,  and 
causes  it  to  be  more  tough ;  because,  if  it  were  pos- 
sible for  the  oil  to  enter  the  pores,  it  would  then 
lessen  the  strength  of  the  attraction  of  cohesion  be- 
tween the  particles,  and  the  tenacity  of  the  steel 
would  be  in  a  measure  destroyed.  The  effect  is  not 
in  the  least  owing  to  the  penetrating  quality  of  the 
oil ;  but  the  effect  is  owing  to  its  imperfectly  con- 
ducting quality,  which  causes  the  steel  to  part  with 
its  heat  so  slowly,  and  the  elevated  temperature  it 
demands  to  be  converted  into  the  vaporous  state. 
A  covering  of  coal  is  also  formed  round  the  steel  by 
the  burned  oil,  which  greatly  retards  the  transmis- 
sion of  heat.  This  slow  rate  of  cooling  is  necessa- 
ry to  favor  a  uniform  degree  of  contraction,  and 
give  the  steel  a  much  longer  time  for  the  rearrange- 
ment of  its  particles,  and  to  make  the  strain  more 


TOUGHENING    OF   STEEL   IN   OIL.  215 

uniform  throughout  the  body  of  the  steel.  Mild 
cast  steel,  after  it  has  been  toughened  in  oil,  may, 
with  well-tempered  tools,  be  turned,  bored,  planed, 
slotted,  chipped,  or  filed  with  pleasure. 

If  cylindrical  or  spherical  mild-steel  shot  could 
be  toughened  in  oil  without  causing  fracture,  a 
more  effective  shot  would  be  the  result ;  but,  owing 
to  the  thickness  and  bulk  of  shot,  it  is  more  than 
probable  that  an  internal  fracture  would  occur  by 
the  contraction  in  cooling.  A  cylindrical-shaped 
shot  made  of  mild  cast  steel  may,  however,  be 
toughened  in  oil  without  causing  fracture,  if  it  be 
first  forged  or  turned  nearly  to  the  required  finished 
dimensions,  and  then  a  hole  made  in  the  centre  in 
the  direction  of  its  length ;  the  hole  need  not  be 
made  completely  through,  but  four  inches  (more  or 
less)  at  one  end  of  the  shot  may  be  left  solid :  this 
will  form  a  kind  of  tube  with  one  solid  end ;  the 
solid  end  will  probably  be  the  best  for  the  rear  end 
of  the  shot.  After  the  hole  is  made  in  the  shot, 
and  it  toughened  in  oil,  and  subsequently  turned 
to  the  required  finished  dimensions,  the  hole  may 
then  be  completely  plugged  up  with  a  plug  made  of 
highly  carbonized  tenacious  cast  steel.  Previous  to 
putting  the  plug  in  its  place,  it  may  be  heated  to  a 
red  heat,  and  quenched  in  oil;  or,  it  may  be 
quenched  in  water  and  used  in  its  then  hard  state, 
but  it  will  probably  be  better  to  reduce  the  hard- 
ness of  it  to  a  brown  or  blue  temper.  The  shot 
may  be  slightly  heated  in  hot  oil,  or  by  any  other 
suitable  means,  in  order  slightly  to  expand  the 
hole  for  shrinking  the  shot  upon  the  plug ;  or,  the 


216  TOUGHENING   OF   STEEL   IN   OIL. 

plug  may  be  forced  into  the  hole  by  hydraulic  pres- 
sure without  heating  the  shot ;  or,  it  may  be  fast- 
ened in  by  running  a  small  portion  of  lead  round 
it.  It  will  be  well,  perhaps,  to  form  a  shoulder 
upon  the  plug,  so  that  it  may  take  a  bearing  on 
some  other  part  of  the  shot,  as  well  as  at  the  bottom 
of  the  hole.  The  front  end  of  this  hard  plug  may 
be  level  with  the  front  end  of  the  shot,  but  experi- 
ments may  prove  it  to  be  better  to  allow  it  to  pro- 
ject a  short  distance  beyond  the  end.  This  hard 
core  will  offer  great  resistance  to  compression,  and 
will  probably  prevent  the  shot  being  flattened  so 
readily  by  the  blow ;  and  tempered  steel  being  more 
elastic  than  untempered  steel,  or  wrought  or  cast 
iron,  it  will  transmit  more  faithfully  the  impulse  it 
receives,  and  the  shot  will  probably  prove  a  more 
destructive  weapon  than  a  cast-steel  solid  shot  in  its 
soft  state,  for  piercing  iron  or  steel  clad  ships.  Ex- 
periments may  perhaps  prove  the  shot  to  be  the 
better  by  having  two  or  more  of  these  tempered 
plugs  let  into  it.  The  toughened  shot  may  per- 
haps answer  well  if  the  hole  were  filled  up  by  pour- 
ing molten  cast  iron  into  it,  the  shot  of  course  to 
stand  in  water  while  the  metal  is  being  poured  in 
the  hole;  the  shot  will  chill  the  cast  iron,  and  the 
water  will  prevent  the  toughness  being  taken  out 
of  the  shot  by  the  heat  of  the  molten  metal.  It  is 
quite  probable  also,  that  a  very  destructive  shot 
may  be  made  by  coiling  a  rod  or  bar  of  iron  round 
one,  two,  or  more  pieces  of  "highly  carbonized  cast 
or  shear  bar  steel ;  then  to  enclose  the  whole  in  an 
iron  or  steel  cylindrical  case  (the  case  to  have  a  solid 


TOUGHENING   OF   STEEL   IN   OIL.  217 

bottom) ;  then  to  braze  the  whole  into  a  solid  mass, 
with  spelter  composed  of  three  parts  copper  and  one 
of  zinc,  or  with  a  more  fusible  kind  of  spelter  if  ne- 
cessary ;  when  cooled  down  to  the  proper  tempera- 
ture to  quench  the  mass  in  oil  or  pure  water,  or 
water  with  a  film  of  oil  upon  its  surface  :  it  would 
also  be  worthy  of  a  trial  in  its  soft  state.  It  may 
be  well  perhaps  to  explain  another  plan ;  it  is  this ; 
to  harden  one,  two,  or  more  pieces  of  bar  steel,  then 
.to  brighten  and  immerse  them  in  solder,  which 
melts  at  a  temperature  suitable  to  coat  their  sur- 
faces with  the  solder,  at  the  same  time  rendering 
the  steel  more  tenacious  by  reducing  the  hard- 
ness. 

After  the  pieces  have  been  coated  with  the 
solder  and  become  cool,  then  shrink  one,  two,  or 
more  iron  or  steel  rings,  in  a  soft  or  tempered  state, 
upon  them,  the  surfaces  of  the  rings  to  be  coated 
with,  solder  in  a  similar  manner  as  the  pieces  of  bar- 
steel  are  coated ;  then  to  enclose  the  whole  in  an 
iron  or  steel  cylindrical  case,  and  subsequently 
solder  the  whole  into  a  solid  mass,  with  solder  of 
suitable  fusibility,  to  suit  the  temper  of  the  steel. 

It  is  quite  probable  that  a  very  destructive  shot 
may  be  made  either  by  welding  a  series  of  rings 
upon  one,  two,  or  more  pieces  of  blister  or  shear 
bar  steel,  or  by  coiling  a  bar  of  iron  round  one, 
two,  or  more  pieces  of  steel,  then  welding  the  whole 
into  a  solid  mass ;  or,  if  this  order  were  reversed, 
iron  inside  and  steel  outside,  it  might  probably 
prove  a  very  destructive  shot:  but  it  is  obvious 

that  there  would  be  greater  difficulty  in  welding 
10 


218  TOUGHENING   OF   STEEL   IN   OIL. 

the  mass.  The  steel  may,  however,  in  this  instance 
be  protected  from  the  direct  action  of  the  fire  by 
coiling  a  thin  bar  of  iron  upon  it ;  then  to  heat  and 
place  the  whole  into  a  strong  die,  and  weld  it  into 
a  solid  mass,  and  subsequently  turning  the  outer 
coil  of  iron  oif  again. 

It  may  perhaps  be  asked  by  those  who  are  not 
practically  acquainted  with  the  hardening  and 
tempering  of  steel,  if  it  would  not  be  better  to 
make  a  solid  shot  entirely  of  highly  x  carbonized 
blister,  shear,  or  cast  steel,  and  subsequently  harden 
and  temper  it.  The  answer  is,  thick  lumps  of 
highly  carbonized  steel,  whether  hardened  in  oil 
or  pure  water,  or  water  with  a  film  of  oil  upon  its 
surface,  cannot  be  hardened  without  becoming  frac- 
tured either  internally  or  externally.  It  must  be 
obvious,  then,  that  the  shot  would  be  less  effective 
in  piercing  iron  or  steel-clad  structures  than  when 
in  a  soft  state. 

Returning  to  the  railway  bars,  I  would  state 
that  I  am  myself  inclined  to  think  that  railway 
bars,  either  of  iron  or  mild  steel,  may  be  made 
more  durable,  without  lessening  their  safety,  by 
heating  them  uniformly  in  a  suitable  furnace  to  a 
bright  red  heat,  and  then  immersing  their  tops  or 
heads  into  some  molten  highly  carbonized  cast 
iron,  and  after  keeping  them  in  the  molten  metal 
for  a  few  minutes,  or  for  a  suitable  time,  which 
could  be  ascertained  by  experiment,  to  quench 
them  in  oil.  By  this  process  the  metal  will  proba- 
bly absorb  carbon ;  consequently,  it  will  then  ac- 
quire a  greater  degree  of  hardness,  and  it  is  quite 


TOUGHENING    OF    STEEL    IN    OIL.  219 

probable  that  their  greater  durability  would  more 
than  compensate  for  the  expense  of  the  process. 

It  would  not  be  impracticable  to  case-harden 
the  heads  of  the  iron  bars  by  cementing  the  heads 
in  animal  charcoal,  and  then  quenching  them  in 
oil ;  but  it  is  questionable  whether  their  greater 
durability  would  compensate  for  the  expense  of 
this  process.  The  bars  would  be  made  more  dur- 
able as  regards  wear  by  cooling  them  in  water; 
but  cooling  them  in  water  would  lessen  their  safety, 
unless  they  were  made  of  very  pure  iron. 


CONCLUSION. 

BEFOEE  I  close  these  details,  I  wish  to  offer  a 
few  sentiments  to  the  consideration  of  the  young 
artist  interested  in  them,  whether  he  is  one  who  is 
anxious  to  excel  in  these  particular  branches  of  art, 
as  affording  the  means  of  honorable  livelihood,  or 
claims  merely  the  appellation  of  an  amateur,  who 
studies  mechanical  operations  from  the  love  of  knowl- 
edge, the  desire  of  amusement,  or  the  hope  of  celeb- 
rity in  making  discoveries  or  improvements.  Let 
him  not  be  discouraged  by  the  failure  of  first  at- 
tempts ;  instead  of  losing  his  time  in  uselessly  re- 
gretting his  disappointment,  let  him  examine  into 
the  cause  of  it,  and  promptly  repeat  his  experi- 
ments with  more  precaution.  It  is  a  mistaken  idea 
that  success  is  absolutely  dependent  upon  length  of 
practice,  uncommon  are  the  cases  in  which  it  fails 
to  be  the  early  reward  of  those  who  persevere;  the 
reward  will  always  be  in  proportion  to  the  amount 
of  perseverance  and  ingenuity  displayed ;  there  are 
always  difficulties  to  contend  with  for  the  young  be- 
ginner. But  in  every  branch  of  art,  if  one  source  of 
experiment  fail,  there  is  abundance  of  other  sources 
still  open.  Further  practical  directions  might  easi- 
ly be  multiplied,  but  the  necessity  for  much  further 
minuteness  of  detail  upon  most  of  the  processes  will 


CONCLUSION.  221 

be  removed  by  a  little  observation,  experience,  and 
perseverance.  But  those  who  postpone  perseverance, 
by  satisfying  themselves  with  the  hope  that  length 
of  practice  will  perfect  them,  will  in  the  end  regret 
their  delusion,  and  may  ineffectually  try  to  recover 
their  loss,  when  habitual  languor,  and  other  injuri- 
ous habits,  have  rendered  the  mind  averse  to  observe, 
and  the  hand  unable  to  perform. 


LIST  OF  WORKS 
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Layard's  Nineveh.    Illustrated. 
Cheap   edition.    Without    Illus- 
trations. 

Learning  to  Spell. 
Le  Brun's  Telemaque. 
Lecky's  Rise. and  Influence  of  Katlon- 

alism.    2  vols. 
Le  Sage's  Adventures  of  Gil  Bias.    1 

vol. 

Gil  Bias,  in  Spanish. 

Letter  Writer. 

Letters  from  Rome. 

Lewes'  (G.  H.)  History  of  Philosophy. 

2  vols. 

In  1  vol. 

Physiology  of  Common  Life. 

Library  of  Travel  and  Adventure.    3 

vols.  in  case. 
Library  for  my  Young  Countrymen. 

9  vols.    in  case. 
Libro  Primario  de  Ortografia. 
Liebig's  Laws  of  Husbandry. 
Life    of    Man    Symbolized    by   the 

Months  of  the  Year. 
Light  and  Darkness 
Lights  and  Shadows  of  New  York 

Picture  Galleries. 
Lindsay's  Poems. 
Linn's  Life  and  Services. 
Little  Builder. 
Little  Engineer. 
Livy,  with  English  Notes. 
Logan's  Chateau  Frissac. 
Looking  Glass  for  the  Mind. 
Lord's  Poems. 

Christ  in  Hades:  a  Poem. 

Louise. 

Lunt's  Origin  of  the  Late  War. 

LyelPs  Elements  of  Geology. 


Lyell's  Principles  of  Geology. 
Lyra  Americana. 
Lyra  Anglicana. 

Macaulay's  Essays.    1  vol. 

Essays.    7  vols. 

Essays.   A  New  and  Revised  Ed* 

tion,  on  tinted  paper.    6  vols. 
Mackintosh's  (Sir  James)  Essays. 
Madge. 
Mahan's  Answer  to  Colenso. 

Numerals  of  Scripture. 

Mahon's  England.    2  vols. 

Maiu's  Novum  Testamentum  Grspce. 

Mandeville's  New  Series  of  Readers. 

1.  Primary  Reader. 

2.  Second  Reader. 

3.  Third  Reader. 

4.  Fourth  Reader. 

5.  Fifth  Reader. 
Mandeville's  Course  of  Reading. 

Reading  and  Oratory. 

First  Spanish  Reader. 

Second  Spanish  Reader. 

Third  Spanish  Reader. 


Magnall's  Historical  Questions. 
Man's  Cry  and  God's  Gracious  Answer. 
Manners'  At  Home  and  Abroad. 


Sedgemoor. 


Manning's  Temporal  Mission  of  the 
Holy  Ghost. 
The  Reunion  of  Christendom. 


Manual  of  Matrimony. 
Markham's  History  of  England. 
Marrayat's  Africa. 

Masterraan  Ready. 

Popular  Novels.    12  vols. 

A  New  and  Revised  Edition, 

printed  on  tinted  paper    12 
vols. 

Marryat's  Settlers  in  Canada. 
Marshall's  (E.  C.)  Book  of  Oratory. 
First  Book  of  Oratory. 


Marshall's  (T.  W.)  Notes  on  Episco- 

Marsh's  Double  Entry  Book-keeping. 

Single  Entry  Book-keeping. 

Bank  Book-keeping. 

Book-keeping  (in  Spanish). 

Blank  Books  for  Double  Entry. 

6  books  in  set. 
Do.  for  Single  Entry.    6  books  in. 

set. 

Martha's  Hooks  and  Eyes. 
Martineau's  Crofton  Boys. 
Peasant  and  Prince. 


Mary  Lee. 

Mary  Staunton. 

Mathews  on  Whist. 

Mayhew's  Illustrated  Horse  Doctor. 

May's  Bertram  Noel. 

Louis'  School  Days. 

Mortimer's  College  Life. 

Sunshine  of  Greystone. 

McCormick's  Visit  to  Sebastopol. 


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